Movement Across the Joints PDF

Movement Across the Joints Movement Across the Joints The type of movement possible across a joint de-pends on the shape of the articulating surfaces, the ligaments, structures around the joint, and the mus-cles that cross the joint. **MOVEMENT ACROSS THE JOINTS** The type of movement possible a...

Movement Across the Joints Movement Across the Joints The type of movement possible across a joint de-pends on the shape of the articulating surfaces, the ligaments, structures around the joint, and the mus-cles that cross the joint. **MOVEMENT ACROSS THE JOINTS** The type of movement possible across a joint de-pends on the shape of the articulating surfaces, the ligaments, structures around the joint, and the muscles that cross the joint (see Figure 3.33). If the articular surfaces are relatively flat, one possible movement is **gliding** (i.e., the articulating sur-faces can move forward and backward or from side to side), similar to moving a book over the surface of the table without lifting the book.  Now, do a small experiment to explore all the other movements possible. Place the pencil or pen in front of you vertically on the table and try these move-ments: Keeping the point of the pencil or pen in con-tact with one point on the table, move the pencil or pen forward and backward. In this movement, the pen moves only in one axis and is similar to the movement of the door in its hinges. Some joints al-low this kind of **monaxial movement.** Next, with the point of the pencil still in contact with one point on the table, move the other end in a circle. This type of movement is known as **circum-duction. **This is the kind of movement your armmakes when you pitch a ball. Try this: Keeping the point on the table, move the pencil so that the part of the pencil that originally faced you faces the opposite side (i.e., rotate it as in using a screwdriver). This movement is known as **ro-tation. **If the bone rotates towards the midline of the body, it is known as **medial, internal,** or **inward ro-tation. **If the rotating movement is away from the midline of the body, it is known as **lateral, external,** or **outward rotation.** These various, experimental movements have been named according to the direction of movement in relation to the anatomic position. The range of motion possible in each joint is described in relation to these terms.  bones For example, keep your arm straight beside you and bend your elbow so that your fingers touch your shoulder. This is flexion at the elbow. Now stand in the anatomic position and reduce the angle between the articulating surfaces of all the joints possible. What is your final position? You should be curled into a ball, with your fingers clenched and toes curled. **Extension **is the opposite movement of flexion, in which the angle between the articulating bones is *in-creased *in the anterior/posterior plane. Extension at the elbow will be bringing your arm to the side of your body after scratching the tip of your shoulder with your fingers. When you stand in the anatomic position, all your joints are extended. In some joints, it is possible to extend the articulating bones beyond the anatomic position. This is known as **hyperexten-sion. **When you move the head to look at the ceiling,you hyperextend your neck. When the articulating bone moves along the frontal/coronal plane, away from the longitudinal axis of the body, the movement is known as **abduc-tion. **Try this. Stand about two feet away from the wall at right angles (i.e., with your side facing the wall). Then put your arm out to touch the wall. Your arm is now abducted at the shoulder. In abduction at the shoulder, the humerus has moved away from the midline along the coronal plane. The opposite of abduction is **adduction,** in which the bone moves *toward* the longitudinal axis. Not all joints can adduct and abduct. Determine all the joints where adduction and abduction is possible. In the hand, the movement of the fingers away from the middle finger (i.e., spreading the fingers) is abduction. Bringing the fingers toward the middle finger is adduction. In the foot, moving away from the second toe is considered as abduction. Because the thumb articulates in a plane at right angles to the other fin-gers, adduction of the thumb moves the thumb to-ward the palm in the sagittal plane. Rotation, as described above, can be medial or lat-eral. At the elbow, the rotatory movements of the ra-dius over the ulna bone are termed **pronation** and **supination. **When the elbow is moved to have the palm of the hand facing the back, it is known as pronation. When the elbow is moved back to the anatomic position---facing the front---it is known as supination. The flexion and extension of the foot have confus-ing terms. According to the terms, you are flexing your foot when you both move the foot up and down, such as in standing on your toes and then lowering yourself to stand on your heel. However, when you stand on your toes, the movement *at the ankle* is re-ferred to as **plantar flexion.** When you stand on your heel, it is known as **dorsiflexion.** There are other movements with specific names. **Inversion **is the movement in which the foot is moved with the sole of the foot facing inward. **Ever-sion **is the opposite movement, in which the foot is moved so that the sole faces outward. A special type of movement is possible in humans because of the unique articulation of the thumb. This movement, which allows us to grasp tiny objects such as holding a pen or picking up a needle from the floor, is known as **opposition,** in which the thumb is able to touch or oppose each of the other fingers. The movement in which you jut your jaw out--- moving the bone anteriorly in the horizontal plane--- is known as **protraction. Retraction** is the opposite of protraction. When the bone moves in a superior/ inferior direction, it is known as **elevation** and **de-pression, **respectively. When you open your mouth, your mandible is depressed and when you close the mouth, the mandible is elevated. The movement in which the trunk is turned to the side, as in bending sideways, is known as **lateralflexion.** Classification of Synovial Joints ================================= Classification of Synovial Joints The synovial joints are classified according to the shapes of the articulating surfaces and the types of movements and range of motion they permit (see Figure 3.34). **CLASSIFICATION OF SYNOVIAL JOINTS** The synovial joints are classified according to the shapes of the articulating surfaces and the types of movements and range of motion they permit (see Figure 3.34). The different subtypes of joints are **balland socket, hinge, pivot, ellipsoidal or condyloid, saddle, **and** gliding **or** planar. **These joints may alsobe classified as **nonaxial, monaxial, biaxial,** and **multiaxial **(or** polyaxial**)** joints, **according to themovements allowed along no axel, one axel, or two or more axels. In nonaxial joints, the movement allowed is not around any axis; in monaxial, the movement is along one axis; in biaxial, along two axes; and in mul-tiaxial, the movement occurs along three or more axes and in directions between these axes.  Ball-and-Socket Joint --------------------- In a ball-and-socket joint, one of the articulating sur-faces is rounded like a ball and the other surface has a depression to fit the ball. These are multiaxial, the most mobile of joints, allowing all types of move-ments---angular and rotational. Therefore, flexion, extension, abduction, adduction, medial and lateral rotation, and circumduction are all possible (e.g., hip joint, shoulder joint) Hinge Joint ----------- The articulating surfaces are somewhat curved in a hinge joint, allowing movement in one plane (monax-ial) similar to the movement of a door. Here, flexion and extension is possible (e.g., elbow joint, knee joint, ankle joint, interphalangeal joint, and joint between the occipital bone and the atlas of the vertebra). Pivot Joint ----------- Here, too, the articulating surfaces permit monaxial movement like the hinge joint, but only rotation is possible (e.g., the joint between the first and second vertebra---the atlas and the axis, and the rotation of the head of radius over the shaft of the ulna proxi-mally). Ellipsoidal or Condyloid Joint ------------------------------ In this biaxial joint, one of the articulating surfaces is oval and fits into a depression in the other articulat-ing surface. Here, movement is possible in two planes. Flexion, extension, adduction, abduction, in-cluding circumduction is possible, but rotation is not (e.g., the articulation between the distal end of radius with the carpal bones, phalanges with the metacarpal bones, and phalanges with the metatarsal bones). Saddle Joint ------------ In this biaxial joint, the articulating surfaces resemble a saddle, being concave in one axis and convex in an-other. It is a modified condyloid joint that allows freer movement. The saddle joint allows angular movements but prevents rotation. Therefore, flexion, extension, ad-duction, abduction, circumduction, and opposition are possible in this joint (e.g., articulation between the carpal bone and metacarpal bone of the thumb). Gliding Joint ------------- The articulating surfaces are flattened or slightly curved and allow sliding movements. These are non-axial joints. The range of motion is slight and rota-tional movements, although possible, are restricted by bones, ligaments and tendons around the joint (e.g., at the ends of clavicle, between carpal bones, between tarsal bones, and between the articulating facets of spinal vertebrae). **Individual Joints** Many of the aches and pain exhibited by clients in a clinic originate from injury and damage to joints and their accessory structures. Those working as part of the health care team treating athletes, deal with ailments related to joints and muscles. Thorough knowledge of the structure of each joint, the range of motion possi-ble, and the muscles that make these movements pos-sible is important to treat such clients. In addition, a scheme for assessing each joint systematically is vital. Each major joint in the body is described in this section in terms of the articular surfaces, type of joint, ligaments, movements possible, range of motion, list of muscles producing movements, an overview of physical assessment, and common ailments. (The in- formation provided below may be more than what is required by some schools of massage therapy. The student is advised to consult the curriculum or their instructors regarding requirements). TemporoMandibular Joint (TMJ) ============================= TemporoMandibular Joint (TMJ) The temporomandibular joint (see Figure 3.35) is af-fected by dysfunction and disease in more than 20% of the population at sometime in their life. **TEMPOROMANDIBULAR JOINT (TMJ)** The temporomandibular joint (see Figure 3.35) is af-fected by dysfunction and disease in more than 20% of the population at sometime in their life. It is a complex joint; its function is affected by multiple structures such as the bones of the skull; mandible; maxilla; hyoid; clavicle; sternum; the joint between the teeth and the alveolar cavities; muscle and soft tissue of the head and neck; and muscles of the cheeks, lips, and tongue. It is affected by the posture of the head and neck and cervical curvature. The joint is used almost continuously for chewing, swal-lowing, respiration, and speech. Imbalance relating to any of the associated structures can affect this joint. Conversely, problems relating to the joint can reflect as dysfunction of any of the associated struc-tures. Hence, dysfunction of this joint is difficult to diagnose and manage.   Articulating Surfaces and Type of Joint --------------------------------------- The mandibular condyle articulates with the mandibu-lar fossa of the temporal bone in this joint (see Figure 3.36). The surface of the fossa is concave posteriorly and convex anteriorly because of the articular emi-nence. The presence of an interarticular disk/carti-lage/meniscus, compensates for the difference in the shapes of the two articular surfaces (the condyle has a convex surface). The disk also divides the joint into a superior and inferior cavity and, because of it, the ar-ticular surfaces of the bones are not in direct contact with each other. The outer edges of the disk are con-nected to the capsule. The joint is strengthened by lig-aments (Figure 3.35B and C). This joint is a combina-tion of a plane and a hinge joint. Diagram Description automatically generated Ligaments --------- The articular capsule, or **capsular ligament,** is a sleeve of thin, loose fibrous connective tissue that surrounds the joint. The **lateral ligament** (**temporo-mandibular ligament**) is a thickening of the capsulelaterally, positioned in the lateral side of the capsule under the parotid glands. It stabilizes the joint later-ally and prevents extensive anterior, posterior, and lateral displacement of the mandibular condyle. The **stylomandibular ligament, **not directly related tothe joint, extends from the styloid process to the pos-terior border of the ramus of the mandible. It pre-vents the mandible from moving forward extensively as when opening the mouth wide. The **spheno-mandibular ligament **stabilizes the joint mediallyand helps suspend the mandible when the mouth is opened wide. Possible Movements ------------------ Depression and elevation of the mandible (hinge joint) and protraction and retraction (gliding joint) are possible. The mandible can also be moved laterally as a result of the presence of the articular carti-lage. The movement of the mandible is a result of the action of both cervical and mandibular muscles. Range of Motion --------------- Normally, three fingers can be inserted into the mouth between the incisor teeth. Muscles ------- Muscles that open (depress) the jaw: *Primary depressors* External (lateral) pterygoid muscle Anterior head of the digastric *Secondary depressors* Gravity Muscles attached to the hyoid bone (suprahyoid muscles---digastric, stylohyoid, mylohyoid, genio-hyoid---and infrahyoid muscles---sternohyoid, thyrohyoid, omohyoid) Muscles that close (elevate) the jaw: *Primary elevators* Masseter Temporalis *Secondary elevators* Internal (medial) pterygoid (Superior head of the lateral pterygoid stabilizes the disk and condylar head during elevation) Muscles that retract the jaw: Posterior fibers of the temporalis Deep fibers of the masseter Digastric Suprahyoids Muscles that protract the jaw: Medial pterygoid Superficial fibers of the masseter Lateral movement: Lateral and medial pterygoid on one side and con-tralateral temporalis muscle assisted by digas-tric, geniohyoid, and mylohyoid Physical Assessment ------------------- A complete history of problems relating to the joint, in-cluding when it started, how it occurred, and previous management is important. History of habitual protru-sion and muscular tension is important. Difficulty opening and closing the mouth, frequent headaches, and abnormal sounds from joints are some symptoms associated with the joint dysfunction. The posture of the person should be examined. Typically, the shoulders are elevated, with the head forward, a stiff neck and back, and shallow, restricted breathing. The area around the joint should be in-spected carefully. The movement of the jaw must be noted to ensure continuous, symmetrical movements. The alignment of the teeth should also be examined. The movements of the condyle of the mandible can be palpated by placing the finger inside the external auditory canal. Clicking sounds may be present if the articular disk is damaged or if there is swelling. The pterygoid muscles can be palpated through the inside of the mouth (disposable gloves should be worn for this procedure). The range of motion---both active and passive---should be checked together with palpation of all relevant muscles for tender points (Refer to books on musculoskeletal assessment for more details). **INTERVERTEBRAL ARTICULATION** Articulating Surfaces and Type of Joint --------------------------------------- Adjacent vertebrae articulate with each other via articular facets located inferiorly and superiorly. This joint is known as the **zygapophyseal joints, interarticular, **or **facet joints** (Figure 3.18). The bodies of the verte-brae also articulate with each other, with most verte-bral bodies, excluding the first and occiput, first and second cervical, and vertebrae of the sacrum and coc-cyx, being separated from each other by the **interver-tebral disks.**  Diagram Description automatically generated The articular surfaces of the vertebral processes are gliding joints, allowing some rotation and flexion. The articulation between the vertebral bodies is a symphyseal joint. The joint between the first cervical vertebra (atlas) and the second vertebra (axis) (**at-lantoaxial joint**) is a pivot joint. The atlas has neither vertebral body nor interverte-bral disk. The axis that projects into the atlas in the re-gion where the vertebral body would be, if present, permits rotation of the ringlike atlas around it, form-ing a pivot joint. Hence, there are two atlantoaxial joints. The medial atlantoaxial joint is between the facet for dens on the atlas and the odontoid process of the axis. The lateral atlantoaxial joint is between the inferior facets of the lateral masses of the atlas and the superior facets of the axis. The superior facet of the lateral masses of the first cervical vertebra---atlas, articulates with the occipital condyles as the **atlanto-occipital joint. **The atlanto-occipital joint allows forflexion, extension, and lateral bending; the atlantoax-ial joints allow flexion, extension, and rotation. Ligaments --------- The bones are held in place by various ligaments. Fig-ure 3.36 shows the various superficial and deep liga-ments related to the atlas, axis, and occiput. The transverse ligament, alar ligament, cruciate, and api-cal ligaments stabilize the upper cervical spine and prevent damage to the brain stem by dislocation of the dens.  Certain ligaments (see Figure 3.37) run between the vertebral bodies and processes to help stabilize the vertebral column. The **anterior longitudinal lig-ament **connects the bodies of adjacent vertebra ante-riorly, while the **posterior longitudinal ligament** does the same posteriorly. The **ligamentum flavum** connects the lamina of adjacent vertebrae. Other lig-aments, known as the **interspinous ligaments,** con-nect adjacent spinous processes. The **supraspinousligament **connects the spinous processes from C7 tothe sacrum. The **intertransverse ligament** connects adjacent transverse processes. Diagram Description automatically generated Possible Movements ------------------ The vertebrae are capable of bending forward (flex-ion), bending backward (hyperextension), and side-ways (lateral flexion and rotation). Range of Motion --------------- Range of motion depends on the angle and size of the articulating surfaces and the resistance offered by the intervertebral disk. It also depends on the muscles and ligaments around the spine. For proper move-ment, remembered that, when one group of muscles (agonists) contract in a direction, the muscles that bring about the opposite movement (antagonists) have to relax. Similarly, the ligaments lying in the op-posite side of the movement have to stretch. The greatest motion possible in the spine is in the lower lumbar region---between L5 and S1, where the joint surfaces are largest and disks the thickest. Con-versely, there is more chance of damage, inflamma-tion (arthritis), and herniation of disks in this region. *Cervical region* Flexion, 45° Extension, 55° Lateral bending, 40° Rotation, 70° *Lumbar region* Flexion, 75° Hyperextension, 30° Lateral and medial bending, 35° Muscles ------- The erector spinae muscles and the ab-dominal muscles help with the various spinal movements. The trapezius, scalenes, sterno-cleidomastoid, and other neck muscles help with movements in the cervical region. The muscles of the cervical spine can be divided into four functional groups: superficial posterior, deep posterior, superficial anterior, and deep anterior. The trapezius is a major superficial posterior muscle. The levator scapulae, splenius capitis, and splenius cervicis are other large superficial muscle groups that extend the head and neck. The multifidi and suboccipital muscles belong to the deep posterior muscle group. The multifidi, which have their origin on the transverse processes and insert into the spinous process above, extend the neck when contracted together and bend the neck to the same side when acting unilaterally. The sternocleidomastoid is the largest and strongest anterior muscle that flexes the neck. Other neck flexors are the scalenus muscles. The deep anterior neck mus-cles are the longus coli and longus capitis. Physical Assessment of the Spine---CervicalRegion ------------------------------------------------- ### *Inspection* The neck, the upper limb, and the upper body should be exposed to examine this region. The position of the head and movement should be noted. ### *Palpation* Bone and cartilage: The bone and cartilage that can be easily palpated are the hyoid bone (superior to the thyroid cartilage), the thyroid cartilage (in men, it forms the Adam's apple), and the mastoid processes and the spinous processes of the cervical vertebrae. The C2 spinous process is the first one that can be palpated as you run your hand down from the oc-ciput. Muscles: The sternocleidomastoid, extending from the sternoclavicular joint to the mastoid process that helps to turn the head from side to side and to flex it, is a common site of injury. Other muscles, such as the trapezius, can be palpated from origin to insertion. The superior nuchal ligament that extends from the occiput to the C7 spinous process can be easily pal-pated as well. Both active and passive range of move-ment of the neck should be tested. Other structures: The cervical chain of lymph nodes may be palpable if enlarged. The parotid gland can also be felt as a boggy, soft swelling over the angle of the mandible if enlarged. The pulsation of the carotid arteries can be easily felt on either side of the trachea. Because the nerves to the upper limb rise from the C5 to T1 spinal cord level, it is important to examine the functioning of the nerves. The function of the nerve can be tested by examining the sensations in the shoulder and the upper limb, as well as the strength of the muscles in the region. Special tests (requiring specific training) test the ligaments of the upper cervical spine. Physical Assessment of the Spine---LumbarRegion ----------------------------------------------- ### *Inspection* Watch for unnatural or awkward movement of the spine or signs of pain when the person exposes the spine when disrobing or walking Look at the skin for swelling, redness, etc. in the region of the spine and identify abnormal curvatures of the spine. ### *Palpation* Bony prominences and ligaments: Posteriorly, feel the spinous processes, posterior superior iliac spine, sacrum, coccyx, iliac crests, ischial tuberosity, and greater trochanter, identifying painful areas. Muscles: Palpate the muscles on either side of the spine and the abdominal muscles. Note tenderness, spasm, or differences in size between the right and left side. Nerve: The sciatic nerve is an important nerve that may get compressed by spinal deformities. Palpate for tenderness in the midpoint between the ischial tuberosity and greater trochanter with the hip flexed. Range of motion: Check flexion by asking the client to lean forward and try to touch the toes with-out bending the knee. Check extension by asking the client to bend backward with your hand on the posterior superior iliac spine. Check lateral bending by asking the client to lean to the right and the left as far as possible. Rotation is checked by turning the trunk to the right and left with the pelvis stabilized. **RIB CAGE ARTICULATIONS** Articulating Surface, Type of Joints,and Ligaments -------------------------------------------------- The ends of the true ribs (1--7) join the costal cartilage anteriorly at **costochondral (sternocostal) joints.** The true ribs are attached to the sternum by individual cartilages; the false ribs (8--10) have a common junc-tion with the sternum. The first rib is joined to the manubrium by a cartilaginous joint and movement is limited. The second rib articulates with a demifacet on the manubrium and body through a synovial plane joint. The cartilages of the third to seventh ribs have small synovial joints that attach to the body of the ster-num. The cartilages of the adjacent false ribs are at-tached to each other at the **interchondral joints.** The ribs and the vertebrae articulate at two locations (see Figure 3.38). The head of each rib articulates with the bodies of two adjacent vertebrae at the costal demi-facet present at the junction of the body and posterior arch of the thoracic vertebrae. The bones are held in place by the **radiate ligament.**A cartilage disk sepa-rates the two articulating surfaces. This synovial joint is known as the **costovertebral joint.**The rib tubercle ar-ticulates with the corresponding vertebral transverse process at the synovial joint (**costotransverse joint**). Costotransverse ligaments hold this joint in place.  The joints between the manubrium and body or sternum---**sternomanubrial joint**---and the body of sternum and xiphoid process---**xiphisternal joint**--- allow little movement. Movements, Range of Motion, and Muscles --------------------------------------- Each rib has its own range and direction of move-ment that differs a little from the others. The first ribs, with their firm attachment to the manubrium, move forward and upward as a unit. The movement occurs at the head of the ribs, with resultant eleva-tion of the manubrium. The other ribs have a typical bucket-handle movement. The false ribs, in addition to elevation of the anterior end, have a caliperlike movement in which the anterior ends are moved laterally and posteriorly to increase the transverse diameter of the thoracic cage. The sidebending and rotation of the thoracic spine is limited by the rib cage and movement possible at the costovertebral, costotransverse, and costochon-dral joints. The rib on the side to which the thoracic vertebra rotates becomes more convex while the op-posite rib becomes flattened posteriorly. **Joints of the Pectoral Girdle and Upper Limb** The bones involved in the function of the shoulder gir-dle include the upper thoracic vertebrae, the first and second ribs, manubrium of the sternum, the scapula, the clavicle, and the humerus. For example, to elevate the arm fully, the scapula needs to rotate, the clavicle must elevate, and the thoracic vertebrae extend along with elevation of the humerus. The scapula serves as a platform on which movements of the humerus are based. The clavicle holds the scapula and humerus away from the body to provide more freedom of move-ment of the arm. Little movement of the humerus is possible without associated actions of the scapula. The movement of the shoulder is facilitated by three joints: 1.        the sternoclavicular joint   2.        the acromioclavicular joint   3.        the shoulder, glenohumeral or scapulohumeral joint and the contact between the scapula and the thoracic cage (this is not a joint)   THE STERNOCLAVICULAR JOINT -------------------------- **(SEE FIGURE 3.39)** ### Articulating Surface and Type of Joint It is formed by the sternal end of the clavicle and the upper lateral part of the manubrium and the superior surface of the medial aspect of the cartilage of the first rib. It is a gliding joint, which has a fairly wide range of movement because of the presence of an articular disk within the capsule. The articular disk helps prevent medial dislocation of the clavicle. It is more common for the clavicle to break or the acromioclavicular joint to dislocate even before a medial dislocation at this joint could occur. Diagram Description automatically generated ### Ligaments Four ligaments---the **anterior sternoclavicular, pos-terior sternoclavicular, interclavicular, **and** costo-clavicular**---support the joint. The attachment of theligaments is self-explanatory. ### Movements, Range of Motion, and Muscles A wide range of gliding movements is possible. The movements are initiated in conjunction with the shoul-der movement. The muscles that move the shoulder also move this joint. ACROMIOCLAVICULAR JOINT ----------------------- ### Articulating Surface and Type of Joint This joint is formed by the lateral end of the clavicle and the acromion of the scapula. It is a planar joint. ### Ligaments The major ligaments are the **superior** and **inferioracromioclavicular ligaments **and the** coracoclavic-ular ligaments **(see Figure 3.40). The latter, althoughsituated away from the joint, provides joint stability. The **trapezoid** and **conoid ligaments** are important for preventing excessive lateral and superior move-ments of the clavicle. They also help suspend the scapula from the clavicle. ### Movements, Range of Motion, and Muscles Little movement takes place in this joint. GLENOHUMERAL JOINT ------------------ ### Articulating Surface and Type of Joint This joint is formed by the head of the humerus and the glenoid fossa of the scapula. It is a ball-and-socket joint and the most freely movable joint in the body. The shallow glenoid fossa is deepened by the presence of a circular band of fibrocartilage, the **glenoidlabrum. **The head of the humerus is prevented tosome extent from upward displacement by the pres-ence of the acromion and coracoid processes of the scapula and the lateral end of the clavicle. A number of ligaments (Figure 3.40A) help stabilize this joint further.  ### Ligaments The **glenohumeral ligament** consists of three thick-ened sets of fibers on the anterior side of the capsule and extends from the humerus to the margin of the glenoid cavity. It prevents excess lateral rotation and stabilizes the joint anteriorly and inferiorly. The **coracohumeral ligament** extends from the coracoid process to the neck of the humerus and strengthens the superior part of the capsule. The **coracoacromial ligament** extends from the coracoid process to the acromion process. The **coracoclavicular** and **acromioclavicular lig-aments **extend to the clavicle from the coracoidprocess and acromion, respectively. The **transverse humeral ligament** extends across the lesser and greater tubercle, holding the tendon of the long head of the biceps in place. ### Bursae Two major and two minor bursae (Fig. 3.40B) are as-sociated with the shoulder joint. The **subdeltoidbursa **is located between the deltoid muscle and thejoint capsule. The**subacromial bursa** and the **sub-coracoid bursa, **as the names suggest, are locatedbetween the joint capsule and the acromion and coracoid processes, respectively. A small **subscapu-lar bursa **is located between the tendon of the sub-scapularis muscle and the capsule. ### Possible Movements Flexion, extension, adduction, abduction, circum-duction, and medial and lateral rotation are all possi-ble in this joint, and many muscles located around the joint help with movement. In addition, the shoul-ders can be elevated, depressed, retracted (scapula pulled together), and protracted (scapula pushed apart as in reaching forward with both arms). For movements to occur at the shoulder, the func-tions of many joints and tissue must be optimal. Some contributing factors are the acromioclavicular joint, sternoclavicular joint, the contact between the scapula and the thorax, and the joints of the lower cervical and upper thoracic vertebrae. For example, the first 15--30° during abduction is a result of the glenohumeral joint. Beyond this, the scapula begins to contribute by moving forward, elevating and rotat-ing upwards, partly a result of movement at the ster-noclavicular and acromioclavicular joints. For every 3° of abduction, 1° occurs at the scapulothoracic ar-ticulation and the other 2° occur at the glenohumeral joint. Abduction using only the glenohumeral joint is possible up to 90°. As the humerus elevates to 120°, the tension devel-oped in the joint capsule laterally rotates the humerus and prevents the greater tubercle from im-pinging on the acromion. At this point, the subdeltoid bursal tissue is gathered below the acromion. (If the bursa is swollen, it can result in restricted movement and/or injury to the tissue). Abduction beyond 160° occurs as a result of movement (extension) at the lower cervical and upper thoracic vertebrae. In uni-lateral abduction, the spine also rotates in the oppo-site direction of the moving arm. ### Range of Motion Flexion, 90° Extension, 45° Abduction, 180° Adduction, 45° Internal rotation, 55° External rotation, 40--45° ### Muscles Many muscles participate in shoulder movement. Of these, the tendons of four muscles provide stability to the joint and are known as the **rotator,** or **musculo-tendinous, cuff. **The four muscles involved are thesupraspinatus, infraspinatus, teres minor, and sub-scapularis (you can remember it by the acronym SITS). The tendons of these muscles blend with the joint capsule. When the arm is hanging at the side, the tension of the superior aspect of the joint capsule is sufficient to keep the two articulating surfaces in contact. When the arm is moved from the side, the rotator cuff muscles must contract to keep the head of the humerus in position. Muscles that help with flexion: *Primary flexors* Deltoid (anterior portion) Coracobrachialis *Secondary flexors* Pectoralis major Biceps brachii Muscles that help with extension: *Primary extensors* Latissimus dorsi Teres major *Secondary extensors* Teres minor Triceps (long head) The muscles that help with abduction: *Primary abductors* Deltoid (middle portion) Supraspinatus *Secondary abductors* Serratus anterior Deltoid (anterior and posterior portions) The muscles that help with adduction: *Primary adductors* Pectoralis major Latissimus dorsi *Secondary adductors* Teres major Deltoid (anterior portion) Muscles that help with internal rotation: *Primary internal rotators* Subscapularis Pectoralis major Latissimus dorsi Teres major *Secondary internal rotator* Deltoid (anterior portion) Muscles that help with external rotation: *Primary external rotators* Infraspinatus Teres minor *Secondary external rotator* Deltoid (posterior portion) Muscles that help elevate the shoulder: *Primary elevators* Trapezius Levator scapulae *Secondary elevators* Rhomboid major Rhomboid minor Muscles that help with scapular retraction (as in the position of attention or bracing the shoulder): *Primary retractors* Rhomboid major Rhomboid minor *Secondary retractor* Trapezius Muscles that help with scapular protraction: *Primary protractor* Serratus anterior ### Physical Assessment It must be remembered that pain in the shoulder and arm could be referred pain from the myocardium, neck, and diaphragm. After inspecting the skin and area around the joint for abnormal swelling, wasting of muscles, or discol-oration of the skin, the bony prominences and the muscles should be palpated for tender points. Then the range of motion should be tested both actively and passively. If a person is unable to move his shoulder joint ac-tively through the normal range of motion, it could be a result of muscle weakness, tightening of the fi-brous tissue of the capsule or ligaments, or abnormal bony growths. Limitations as a result of muscle weakness can be ruled out if full range of movement is achieved by moving the joint passively. If the limi-tation persists even when moving the joint passively, the problem is probably a result of ligaments, cap-sule, or bony growths. THE ELBOW JOINT --------------- ### Articulating Surfaces and Type of Joint The elbow joint (see Figure 3.41) is a hinge joint with three components. The **humeroulnar joint** is where the trochlea of the humerus articulates with the trochlear notch of the ulna. The **humeroradial joint** is formed by the capitulum of the humerus and the head of the radius, and the **proximal radioulnarjoint **is the articulation between the head of the ra-dius and the radial notch of the ulna. The latter is not part of the hinge but is a pivot joint. The capsule and joint cavity are continuous for all three joints. The el-bow joint is relatively stable because it is well sup-ported by bone and ligaments. Diagram Description automatically generated ### Ligaments Two major ligaments---the **ulnar (medial) collateral ligament **and the** radial (lateral) collateral liga-ment**--- support the joint on either side and rise from the medial and lateral epicondyle of the humerus, re-spectively. The head of the radius is held in the radial notch of the ulna by the **annular ligament.** ### Bursa An **olecranon bursa** is located posteriorly over the olecranon process. ### Possible Movements The elbow joint allows flexion and extension. Fore-arm supination and pronation are also possible and a result of the articulation between the radius and ulna proximally and distally. ### Range of Motion Flexion, 135° Extension, 0--5° Supination, 90° Pronation, 90° ### Muscles Muscles that flex the elbow: *Primary flexors* Brachialis Biceps brachii *Secondary flexors* Brachioradialis Supinator Muscles that help with extension: *Primary extensor* Triceps *Secondary extensor* Anconeus Muscles that help with supination: *Primary supinators* Biceps Supinator *Secondary supinator* Brachioradialis Muscles that help with pronation: *Primary pronators* Pronator teres Pronator quadratus *Secondary pronator* Flexor carpi radialis ### Physical Assessment #### Inspection Note the angle made by the forearm with the upper arm---the **carrying angle.** Normally, it is about 5° in men and 10--15° in women. Swelling, scars, and skin discolorations should be recorded. #### Palpation The bony prominences that can be easily felt at the el-bow are the medial epicondyle, the olecranon, the olecranon fossa of the humerus into which the ole-cranon fits, the ulnar border, the lateral epicondyle, and the head of the radius. Medially, the ulnar nerve can be easily located in the sulcus between the medial epicondyle and the olecranon process. If the olecranon bursa is inflamed, it can be felt as a thick and boggy structure over the olecranon. Tenderness over the lateral collateral liga-ment and the annular ligament can be identified. The shallow depression in front of the forearm is the cubital fossa. The biceps tendon and the pulsa-tion of the brachial artery can be felt here. In addition, the various muscles, active and pas-sive range of motion should be checked. DISTAL (INFERIOR) RADIOULNAR JOINT ---------------------------------- This pivot joint anchors the distal radius and ulna and participates in supination and pronation. It has a joint capsule independent of the wrist joint. See above for muscles that help with supination and pronation. MIDDLE RADIOULNAR JOINT ----------------------- This is syndesmosis and includes the interosseous membrane and the oblique cord that runs between the interosseous border of the radius and ulna. The oblique cord prevents displacement of the radius when the arm is pulled. The interosseus membrane provides stability to the elbow and radioulnar joints transmits force from hand and provides surface for muscle attachment. JOINTS OF THE WRIST AND HAND ---------------------------- Many joints are present in the region of the wrist and hand (see Figure 3.42). These include the distal ra-dioulnar joint, radiocarpal joint (wrist joint), inter-carpal joints, midcarpal joint, carpometacarpal joints, intermetacarpal joints, metacarpophalangeal joints, and interphalangeal joints.  THE WRIST JOINT (RADIOCARPAL JOINT) ----------------------------------- ### Articulating Surfaces and Type of Joint The wrist is a condyloid joint formed by the articula-tion between three carpal bones (scaphoid, lunate, and triquetrum) with the distal end of the radius and an articular disk. The articular disk separates the ulna from the carpals, making the distal radioulnar joint distinct from the radiocarpal joint. ### Ligaments Many ligaments (Figure 3.42B), such as the **palmar** and **dorsal ulnocarpal** and **radiocarpal ligaments,radial collateral ligaments, **and** ulnar collateral ligaments,**stabilize the joint and the carpal bones inthis region. They also ensure that the carpals follow the radius during pronation and supination. Diagram Description automatically generated An important ligament in the hand complex is the **transverse carpal ligament, **or the** flexor retinacu-lum. **The transverse carpal ligament forms the roofof the palmar arch formed by the carpals (see Figure 3.43). The hook of the hamate and the pisiform form the ulnar side of the arch and the trapezium and the radial side of the scaphoid form the radial side. The tendons of the flexor digitorum superficialis and flexor digitorum profundus, surrounded by a com-mon synovial sheath, pass through the carpal tunnel. The tendon of the flexor carpi radialis, the tendon of flexor pollicis longus, and the median nerve also pass through the tunnel.   ###   Possible Movements The wrist allows flexion, extension, abduction (radial deviation), adduction (ulnar deviation), and circum-duction of the hand. ### Range of Motion Ulnar deviation, 30° Radial deviation, 20° Flexion, 80° Extension, 70° ### Muscles The muscles that move the hand pass over the wrist joint and help move it. There are 6 flexors and 2 pronators on the anterior or flexor surface of the forearm and a total of 12 muscles on the extensor surface of the forearm. The abductor pollicis longus and the flexor and extensor carpi radialis longus and brevis help with radial deviation. The flexor and ex-tensor carpi ulnaris help with ulnar deviation. OTHER JOINTS OF THE HANDS ------------------------- There are many joints in the region of the hand (Fig-ure 3.42) as there is articulation between the various carpal bones. These are gliding joints. A saddle joint is present between the proximal end of the first metacarpal and the trapezium that allows all the movements of the thumb. The carpometacarpal joint (between hamate and metacarpal bone) of the lit-tle finger is also a saddle joint. The carpometacarpal joints of the remaining fingers are plane joints that permit little or no movement. The function of the car-pometacarpal joints is primarily to allow cupping of the hand around the shape of objects. The joints between the metacarpal bones and the phalanges---the metacarpophalangeal joints---are of the condyloid type, allowing flexion, extension, ab-duction, adduction, and some axial rotation. Flexion and extension is more extensive. Some hyperexten-sion is also possible at these joints. The joints be-tween the phalanges---interphalangeal joints---are of the hinge type, allowing flexion and extension. The joint between the phalanges of the thumb also allow some axial rotation. ### Range of Motion Flexion and extension at the various joints are dif-ferent. Metacarpophalangeal joints: flexion, 90°; extension, 30--45° Proximal interphalangeal joint: flexion, 100°; exten-sion, 10° Distal interphalangeal joint: flexion, 90°; extension, 10° Adduction and abduction of fingers: 20° Because the thumb articulates at right angles to the rest of the fingers the movements of the thumb is different. The carpometacarpal joint (trapezium-thumb metacarpal joint) of the thumb is a saddle joint that is mobile and allows all movements, in-cluding circumduction. Metacarpophalangeal joint of thumb: adduction, 50°; flexion, 90°; extension, 20°; abduction, 70°. It is also possible to oppose the thumb. Minimal axial ro-tation is also possible at this joint. ### Physical Assessment #### Inspection The dorsal and palmar surfaces should be examined and the way the hand is held should be noted. Nor-mally, the fingers are held parallel to each other in a slightly flexed position. Damage to nerves supplying the hand produces typical deformities. #### Palpation The various bones can be easily felt through the skin and may be palpated for tender points. Both active and passive range of motion should also be tested. **Joints of the Pelvic Girdle and Lower Limbs** The joints of the pelvic girdle (see Figure 3.44) must be considered in conjunction with the joints of the lower lumbar region and hips because dysfunction of any one structure can affect the function of all others. For example, fusion of the lower lumbar vertebrae, differ-ences in leg length, and stiffening of any of these joints can result in pain and stress on other structures.  Therefore, the structures of this region are often referred to as the lumbopelvic complex, which in-cludes the fourth and fifth lumbar joints, the sacroil-iac joints, sacrococcygeal joint (symphysis), the hip joints, and the pubic symphysis. A major function of the pelvic girdle is to transmit the weight of the upper body to the lower limbs and forces from the lower limb to the upper body. The sacroiliac joints are important for walking by absorb-ing forces from the leg and protecting the disks. SACROILIAC JOINT ---------------- In osteopathic medicine, the sacroiliac joint is con-sidered as two joints---the sacroiliac joint (where the sacrum moves in relation to the ilium) and iliosacral joint (where the ilium moves in relation to the sacrum). This is so because the sacrum is associated with the spine and helps transmit forces from above to the pelvis, and the ilium is closely associated with the lower limb and transmits forces upwards. ### Articulating Surfaces and Type of Joint The two synovial joints between the medial surface of the ilium and the lateral aspect of the upper sacral vertebrae are L-shaped when viewed laterally. The ar-ticular surfaces are covered with cartilage and marked by elevations and depressions that fit each other and make the joint stronger. ### Ligaments The ligaments that bind the sacrum to the ilium withstand the major forces through the sacroiliac joints. They form a network of fibrous bands. Many ligaments---**iliolumbar, sacrolumbar, sacroiliac** (an-terior and posterior), **sacrotuberous** (sacrum to is-chial tuberosity), and **sacrospinous**---are found around the joints (Figure 3.44). Of these, the iliolum-bar, which extends from the transverse process of the 5th vertebrae to the posterior iliac crest, is the most important as it stabilizes the 5th vertebrae on the sacrum. In addition, the muscles adjacent to the joint---gluteus maximus, gluteus minimus, piriformis, latissimus dorsi, quadratus lumborum, and iliacus--- have fibrous attachments that blend with the liga-ments and make the joints even stronger. ### Possible Movements and Range of Motion The movements of this joint are limited, but even this limited movement is important. The main function of this joint is to serve as a shock absorber. The move-ment of the sacrum is described as flexion (nutation) and extension (counter-nutation). During flexion the sacral promontory moves anteriorly and inferiorly with the apex moving posteriorly, while the iliac bones approximate and the ischial tuberosities move apart. Such a movement occurs when walking and when bending forward (flexion) and backward (exten-sion). During walking, the movement of the sacrum is determined by the forces from above, while the move-ment of the ilium is determined by the femur. ### Muscles Though this joint is surrounded by strong muscles, none play a direct part in moving the sacrum. Sacral movement is a result of the pull of forces through lig-aments and gravity. By pulling on the ilia, the muscles in the vicinity have an indirect effect on the sacrum. There are 35 muscles attached to the sacrum or hipbones and, together with the ligaments and fascia, they help coordinate movement of the trunk and lower limbs. Problems associated with any of them can result in alteration of the mechanics of the pelvis. The quadratus lumborum, erector spinae, abdominal muscles, rectus femoris, iliopsoas, tensor fascia latae, piriformis, short hip adductors, hamstrings, gluteus maximus, medius and minimus, vastus medialis and lateralis, the pelvic floor muscles are important mus-cles that must be considered in a client with low back pain. ### Physical Assessment When assessing this joint, it is important to take a good history that includes history of trauma and ab-normal stress to the region. Typically, the pain arising from this joint is unilateral, increased by walking, get-ting off the bed, and climbing stairs, etc. Examination of this joint should be done in conjunction with the hip joint and lumbar spine as the pain may be re-ferred to this joint from those areas. Description of in-dividual tests used for assessing this joint is beyond the scope of the book. The gait, posture, alignment of bony structures, difference in leg length, and passive and active movements should be tested, and treat-ment aimed at normalizing the stresses on the lum-bopelvic complex should be based on the findings. THE HIP JOINT ------------- ### Articulating Surfaces and Type of Joint The hip joint, also referred to as the **acetabulofemoral** or **iliofemoral joint,** is one of the most stable joints be-cause the articular surfaces of the rounded head of the femur and the acetabulum of the pelvis fit well into each other. The acetabulum is further deepened by the fibrocartilage (**acetabular labrum**) located in the ac-etabulum. In addition to shape of the articular surface, the hip joint, similar to the shoulder, has supporting ligaments (see Figure 3.45). Diagram Description automatically generated ### Ligaments and Bursa The thick capsule is reinforced by strong ligaments. The **iliofemoral ligament** is a thick band that runs between the anterior inferior iliac spine and the in-tertrochanteric line of the femur. This ligament pre-vents excessive internal and external rotation. When standing, this ligament is twisted and pulled taut and results in "locking" of the joint, allowing the person to stand with little muscle action. The **pubofemoralligament **extends from the pubic portion of the ac-etabular rim to the inferior portion of the neck of the femur. The **ischiofemoral ligament** runs between the ischial acetabular rim and the superior portion of the femoral neck.  The **transverse acetabular liga-ment **runs between the gap in the inferior margin ofthe acetabular labrum. Another ligament, the **liga-mentum teres, **is located inside the joint capsule andruns between the acetabular notch and a small de-pression (fovea capitis) located in the femoral head. A few bursae surround the hip joint. The **il-iopectineal bursa **lies on the anterior aspect of thehip joint, deep to the iliopsoas muscle, as it crosses the joint. It may communicate with the joint cavity of the hip joint. The **trochanteric bursae**lie over the greater trochanter, deep to the gluteus maximus, re-ducing friction between the bone and muscle. ### Possible Movements The hip permits flexion, extension, adduction, abduc-tion, medial rotation, lateral rotation, and some cir-cumduction. ### Range of Motion Abduction, 45--50° Adduction, 20--30° External/lateral rotation, 45° Internal/medial rotation, 35° Flexion, 135° Extension, 30° ### Muscles The action of most muscles around the hip can be de-termined from the location. The flexor muscles are located in the anterior quadrant, the extensors in the posterior quadrant, the adductors in the medial, and the abductors in the lateral quadrant. Muscles that flex the hip: *Primary flexor* Iliopsoas *Secondary flexors* Rectus femoris Sartorius Muscles that extend the hip: *Primary extensor* Gluteus maximus *Secondary extensor* Hamstrings Muscles that abduct the hip: *Primary abductor* Gluteus medius *Secondary abductors* Gluteus minimus Tensor fascia lata Muscles that adduct the hip: *Primary adductor* Adductor longus *Secondary adductors* Adductor brevis Adductor magnus Pectineus Gracilis Muscles that rotate the hip laterally: Gluteus maximus Gluteus medius and minimus (posterior fibers) Muscles that rotate the hip medially: Adductor magnus, longus, brevis Gluteus medius and minimus (anterior fibers) Iliopsoas ### Physical Assessment #### Inspection The gait should be observed as the person enters the room. It is preferable to have the patient's body ex-posed waist down. When standing normally, the an-terior superior iliac spine should be level with a slight anterior curvature of the lumbar spine. Absence of the lumbar lordosis may indicate spasm of the mus-cles. Weakness of the abdominal muscles may exhibit an abnormally increased lordosis. Look for muscle wasting and body asymmetry. #### Palpation Bony prominences: Various bony prominences can be easily palpated. These are the anterior superior iliac spines, iliac crest, greater trochanter, and pubic tu-bercles anteriorly. Posteriorly, the posterior superior iliac spine and the ischial tuberosity can be palpated. Other structures: The inguinal ligament, which runs between the anterior superior iliac spine and the pubic tubercle, marks part of the route taken by the male testis as it descends into the scrotum. Bulges in this region may indicate an inguinal hernia. The femoral artery pulsation can be felt just inferior to the inguinal ligament. The femoral vein lies just me-dial to the artery. Tenderness over the sciatic nerve as it emerges from the sacral region can be palpated. The active and passive range of motion of the hip should be tested as well, together with discrepancies between the two legs. **THE KNEE JOINT** Articulating Surfaces and Type of Joint --------------------------------------- The knee joint, or tibiofemoral joint, (see Figure 3.46) is one of the largest, most complex, and most frequently injured joints in the body and a thorough knowledge of its anatomy is important. It is a hinge joint. The fibula does not articulate with the femur and comes in con-tact only with the lateral surface of the tibia.  The lower end of the femur, with its condyles and deep fossa between them, articulates with the flat up- per surface of the tibia. Numerous ligaments, carti-lages, and tendons help stabilize this joint. The articu-lating surface is deepened by the presence of two half-moon--shaped fibrocartilage disks---the **medial** and **lateral meniscus**---located on the tibia (Figure 3.46E).The menisci also serve as shock absorbers, spreading the stress on the joint over a larger joint surface and helping lubricate the joint and reduce friction. Ligaments --------- The knee joint has ligaments located inside and outside the joint capsule. Inside the joint, there are two liga-ments that run anteroposteriorly, preventing excessive forward and backward movement. The **anterior cruci-ate ligament **runs from the anterior part of the tibia tothe medial side of the lateral femoral condyle. It pre-vents excessive forward movement (hyperextension) of the tibia. The **posterior cruciate ligament** extends su-periorly and anteriorly from the posterior aspect of the tibia to the lateral side of the medial condyle. It pre-vents the tibia from slipping backward and, with the popliteus muscle, it prevents the femur from sliding anteriorly over the tibia in a squatting position. The **patellar tendon**---a thick, fibrous band that extends from the patella to the tibial tuberosity---is actually an extension of the quadriceps tendon that stabilizes the joint anteriorly. Thin fibrous bands--- **patellar retinaculum**---extend from the side of thepatella to the tibial condyles. Posteriorly, the capsule is thickened to form the **oblique popliteal ligament,** an extension of the semimembranous tendon. An-other thickening---the **arcuate popliteal ligament**--- runs from the posterior fibular head to the capsule. Medially, the **medial collateral ligament,** or the **tibial collateral ligament, **runs from the medial epi-condyle of the femur to the medial surface of the tibia. This ligament helps stabilize the joint medially and prevents anterior displacement of the tibia on the femur. Another ligament---**lateral collateral ligament,** or the **fibular collateral ligament,** runs from the lateral epicondyle of the femur to the head of the fibula, sta-bilizing the joint laterally. Other small ligaments ex-ist. The **coronary ligament** attaches the menisci to the tibial condyle, the **transverse ligament** connects the anterior portions of the medial and lateral menisci, and the **meniscofemoral ligament** runs posteriorly, joining the lateral menisci to the medial condyle of the femur. In addition to the support provided by the liga-ments, the joint is stabilized medially by the **pes anser-inus tendons **(semitendinosus, gracilis, and sartorius)and the semimembranosus tendon. The posterolateral region is supported by the biceps femoris tendon, and the posterior aspect is reinforced by the origins of the gastrocnemius muscles and the popliteus muscles. Bursae ------ The knee joint is surrounded by numerous bursae. The largest is the **suprapatellar bursa,** or **quadri-ceps bursa, **an extension of the joint capsule that al-lows movement of the thigh muscles over the lower end of the femur. Subcutaneous bursae---the **subcu-taneous **or** superficial prepatellar **and** infrapatel-lar bursa **and the** deep infrapatellar bursa**---sur-round the patella. A large fat pad, the infrapatellar fat pad, exists deep to the patella tendon. The fat pad is lined on the deep surface by synovial membrane and is thought to help lubricate the joint as it deforms during flexion and extension of the knee. In addition to the above, bursae exist in the popliteal fossa---**popliteal bursa**---and near the gas-trocnemius---the **gastrocnemius bursa.** The **semi-membranous bursa,**which lies deep to the semi-membranosus tendon and the medial origin of the gastrocnemius muscle, often communicates with the joint. Other bursae may exist between the pes anser-inus and the iliotibial band. Possible Movements ------------------ The knee joint allows flexion (with an associated glide), extension (with an associated glide), and in-ternal and external rotation. Active rotation of the knee occurs only when the knee is flexed. Range of Motion --------------- Flexion, 135° Extension, 0° Internal rotation, 10° External rotation, 10° Muscles ------- Muscles that flex the knee: Hamstrings: semimembranosus, semitendinosus, biceps femoris Muscle that extends the knee: *Primary extensor* Quadriceps Muscles that rotate the knee medially: Semitendinosus Semimembranosus Muscle that rotates the knee laterally: Biceps femoris Physical Assessment ------------------- ### *Inspection* The gait of the individual must be closely watched. Identify abnormal swellings and asymmetry of mus-cles. The knee should be fully extended while standing. ### *Palpation* Many parts of the bones can be easily palpated in and around the knee. The medial and lateral femoral condyle, the head of the fibula and the patella, and others may be palpated. The muscles and tendons in and around the joint should be palpated for tender-ness. Enlarged bursae (a common ailment) can be felt as a boggy, soft swelling. Tenderness in the joint margins may be a result of tears in the medial and lateral meniscus. The medial and lateral collateral ligaments are also easily palpated. The insertion of the tendons of the sartorius, gracilis, and semitendi-nosus can be palpated on the medial aspect of the joint. The iliotibial tract, a thick fibrous band, runs on the lateral aspect of the knee joint. In the popliteal fossa, the pulsation of the popliteal artery can be felt. The stability of the joint must be tested by check-ing the collateral and cruciate ligaments. The range of motion should also be tested actively and passively. Diagram Description automatically generated The lower end of the femur, with its condyles and deep fossa between them, articulates with the flat up- per surface of the tibia. Numerous ligaments, carti-lages, and tendons help stabilize this joint. The articu-lating surface is deepened by the presence of two half-moon--shaped fibrocartilage disks---the **medial** and **lateral meniscus**---located on the tibia (Figure 3.46E).The menisci also serve as shock absorbers, spreading the stress on the joint over a larger joint surface and helping lubricate the joint and reduce friction. ### Ligaments The knee joint has ligaments located inside and outside the joint capsule. Inside the joint, there are two liga-ments that run anteroposteriorly, preventing excessive forward and backward movement. The **anterior cruci-ate ligament **runs from the anterior part of the tibia tothe medial side of the lateral femoral condyle. It pre-vents excessive forward movement (hyperextension) of the tibia. The **posterior cruciate ligament** extends su-periorly and anteriorly from the posterior aspect of the tibia to the lateral side of the medial condyle. It pre-vents the tibia from slipping backward and, with the popliteus muscle, it prevents the femur from sliding anteriorly over the tibia in a squatting position. The **patellar tendon**---a thick, fibrous band that extends from the patella to the tibial tuberosity---is actually an extension of the quadriceps tendon that stabilizes the joint anteriorly. Thin fibrous bands--- **patellar retinaculum**---extend from the side of thepatella to the tibial condyles. Posteriorly, the capsule is thickened to form the **oblique popliteal ligament,** an extension of the semimembranous tendon. An-other thickening---the **arcuate popliteal ligament**--- runs from the posterior fibular head to the capsule. Medially, the **medial collateral ligament,** or the **tibial collateral ligament, **runs from the medial epi-condyle of the femur to the medial surface of the tibia. This ligament helps stabilize the joint medially and prevents anterior displacement of the tibia on the femur. Another ligament---**lateral collateral ligament,** or the **fibular collateral ligament,** runs from the lateral epicondyle of the femur to the head of the fibula, sta-bilizing the joint laterally. Other small ligaments ex-ist. The **coronary ligament** attaches the menisci to the tibial condyle, the **transverse ligament** connects the anterior portions of the medial and lateral menisci, and the **meniscofemoral ligament** runs posteriorly, joining the lateral menisci to the medial condyle of the femur. In addition to the support provided by the liga-ments, the joint is stabilized medially by the **pes anser-inus tendons **(semitendinosus, gracilis, and sartorius)and the semimembranosus tendon. The posterolateral region is supported by the biceps femoris tendon, and the posterior aspect is reinforced by the origins of the gastrocnemius muscles and the popliteus muscles. ### Bursae The knee joint is surrounded by numerous bursae. The largest is the **suprapatellar bursa,** or **quadri-ceps bursa, **an extension of the joint capsule that al-lows movement of the thigh muscles over the lower end of the femur. Subcutaneous bursae---the **subcu-taneous **or** superficial prepatellar **and** infrapatel-lar bursa **and the** deep infrapatellar bursa**---sur-round the patella. A large fat pad, the infrapatellar fat pad, exists deep to the patella tendon. The fat pad is lined on the deep surface by synovial membrane and is thought to help lubricate the joint as it deforms during flexion and extension of the knee. In addition to the above, bursae exist in the popliteal fossa---**popliteal bursa**---and near the gas-trocnemius---the **gastrocnemius bursa.** The **semi-membranous bursa,**which lies deep to the semi-membranosus tendon and the medial origin of the gastrocnemius muscle, often communicates with the joint. Other bursae may exist between the pes anser-inus and the iliotibial band. ### Possible Movements The knee joint allows flexion (with an associated glide), extension (with an associated glide), and in-ternal and external rotation. Active rotation of the knee occurs only when the knee is flexed. ### Range of Motion Flexion, 135° Extension, 0° Internal rotation, 10° External rotation, 10° ### Muscles Muscles that flex the knee: Hamstrings: semimembranosus, semitendinosus, biceps femoris Muscle that extends the knee: *Primary extensor* Quadriceps Muscles that rotate the knee medially: Semitendinosus Semimembranosus Muscle that rotates the knee laterally: Biceps femoris ### Physical Assessment #### Inspection The gait of the individual must be closely watched. Identify abnormal swellings and asymmetry of mus-cles. The knee should be fully extended while standing. #### Palpation Many parts of the bones can be easily palpated in and around the knee. The medial and lateral femoral condyle, the head of the fibula and the patella, and others may be palpated. The muscles and tendons in and around the joint should be palpated for tender-ness. Enlarged bursae (a common ailment) can be felt as a boggy, soft swelling. Tenderness in the joint margins may be a result of tears in the medial and lateral meniscus. The medial and lateral collateral ligaments are also easily palpated. The insertion of the tendons of the sartorius, gracilis, and semitendi-nosus can be palpated on the medial aspect of the joint. The iliotibial tract, a thick fibrous band, runs on the lateral aspect of the knee joint. In the popliteal fossa, the pulsation of the popliteal artery can be felt. The stability of the joint must be tested by check-ing the collateral and cruciate ligaments. The range of motion should also be tested actively and passively. **TIBIOFIBULAR JOINT (PROXIMAL AND DISTAL)** The superior or proximal tibiofibular joint is a plane synovial joint formed by the head of the fibula and the posterolateral surface of the tibia (see Figure 3.47). The synovial cavity is often continuous with the knee joint, allowing slight superior and inferior glide and anteroposterior glide and rotation of the fibula.  The tibia and fibula are bound together by the in-terosseous membrane that separates the leg into an-terior and posterior compartments. The inferior tibiofibular joint is a syndesmosis formed by the articulation of the fibula with the lat-eral aspect of the distal end of the tibia. The joint is reinforced by the anterior and posterior tibiofibular ligaments. The Ankle Joint and Joints of the Foot ====================================== The Ankle Joint and Joints of the Foot The ankle joint (see Figure 3.48) is formed by the dis-tal end of the tibia, fibula, and the superior surface of the talus. **THE ANKLE JOINT AND JOINTS OF THE FOOT** Articulating Surfaces and Type of Joint --------------------------------------- The ankle joint (see Figure 3.48) is formed by the dis-tal end of the tibia, fibula, and the superior surface of the talus. This joint is also known as the **talocrural joint. **It is a hinge joint with the lateral and medialaspect of the capsule thickened to form ligaments.  Other articulations (see Figure 3.49) occur between the talus and calcaneus (**subtalar joint**); between the tarsal bones (**midtarsal joints**) and talocalcaneonav-icular and calcaneocuboid joints; between the ante-rior tarsals (**anterior tarsal joints**) and the cubonav-icular , cuneonavicular, cuneocuboid, and intercuboid joints; between the tarsals and the metatarsals (**tar-sometatarsal joints**); between the metatarsal andphalanges (**metatarsophalangeal joint**); and be-tween the phalanges (the **proximal** and**distal inter-phalangeal joints**). Diagram Description automatically generated Ligaments --------- The **medial ligament,** or the **deltoid ligament,** is a thickening of the medial fibrous capsule that attaches the medial malleolus to the navicular, calcaneus, and talus bones. The **calcaneofibular ligament** extends from the lateral malleolus to the calcaneus. Anteri-orly and posteriorly, ligaments extend from the lat-eral malleolus to the talus to form the **anteriortalofibular **(most frequently injured) and** posterior talofibular ligaments. **The various ligaments pre-vent tilt and rotation of the talus and forward and backward movement of the leg over the talus. Possible Movements ------------------ The ankle allows dorsiflexion and plantar flexion. However, the subtalar joint and tarsal joints allow further movement. Eversion and inversion is possible at the subtalar joint. The foot can be adducted and abducted at the midtarsal joints. The metatarsopha-langeal joints and interphalangeal joints are hinge joints, allowing flexion and extension of the toes. Range of Motion --------------- Dorsiflexion, 20° Plantar flexion, 50° Inversion and eversion, 5° Adduction, 20° Abduction, 10° Flexion (toes), 45° Extension, 70--90° Muscles ------- Muscles that cause plantar flexion: *Primary plantar flexors* Gastrocnemius Soleus *Secondary plantar flexors* Tibialis posterior Flexors of the toes Peroneus longus and brevis Muscles that cause dorsiflexion: Tibialis anterior Peroneus tertius Extensors of the toes Muscle that inverts the foot: Tibialis anterior and posterior Muscle that everts the foot: Peroneus longus, brevis, and tertius Physical Assessment ------------------- ### *Inspection* The external appearance of the shoe and foot should provide information. The alignment of the toes and the shape of the foot and arches should be inspected. The color of the skin and presence of swelling should also be noted. ### *Palpation* The bones of the foot and ankle are easily palpated. Some bony prominences that can be located are the malleoli, talus, calcaneus, and the metatarsal and phalanges. The deltoid ligament is also palpable infe-rior to the medial malleolus. The long saphenous vein, if dilated may be visible just anterior to the me-dial malleolus. Both active and passive range of mo-tion should be tested at the various joints.  The tibia and fibula are bound together by the in-terosseous membrane that separates the leg into an-terior and posterior compartments. The inferior tibiofibular joint is a syndesmosis formed by the articulation of the fibula with the lat-eral aspect of the distal end of the tibia. The joint is reinforced by the anterior and posterior tibiofibular ligaments. THE ANKLE JOINT AND JOINTS OF THE FOOT -------------------------------------- ### Articulating Surfaces and Type of Joint The ankle joint (see Figure 3.48) is formed by the dis-tal end of the tibia, fibula, and the superior surface of the talus. This joint is also known as the **talocrural joint. **It is a hinge joint with the lateral and medialaspect of the capsule thickened to form ligaments. Diagram Description automatically generated Other articulations (see Figure 3.49) occur between the talus and calcaneus (**subtalar joint**); between the tarsal bones (**midtarsal joints**) and talocalcaneonav-icular and calcaneocuboid joints; between the ante-rior tarsals (**anterior tarsal joints**) and the cubonav-icular , cuneonavicular, cuneocuboid, and intercuboid joints; between the tarsals and the metatarsals (**tar-sometatarsal joints**); between the metatarsal andphalanges (**metatarsophalangeal joint**); and be-tween the phalanges (the **proximal** and**distal inter-phalangeal joints**). **ARCHES OF THE FOOT** The foot has three major arches that help distribute the weight of the body between the heel and the ball of the foot during standing and walking. Two longitudinal---the **medial** and the **lateral longitudinal arch**--- and one transverse---the **transverse arch**---exist. The shape of the arch is maintained by ligaments, the ten-dons attached to the foot, and the configuration of the bones. The medial arch is formed by the calcaneus, talus, navicular, cuneiforms and the medial three metatarsal bones. The lateral arch is formed by the calcaneus, cuboid, and the two lateral metatarsals. The transverse arch is formed bby the cuboid and cuneiform bones. **Age-Related Changes on the Skeletal System and Joints** The slower movement, weakness, and altered physi-cal appearance are a result of changes in the muscu-loskeletal system. With age, there is a decrease in height as a result of the shortening of the vertebral column. The inter-vertebral disks and the vertebrae decrease in height. The continued growth of nose and ear cartilage makes them larger. Subcutaneous fat tends to be re-distributed with more in the abdomen and hips and less in the extremities. This redistribution makes the bony landmarks more prominent with deepening hollows in the axilla, shoulders, ribs, and around the eyes. The ground substance, in relation to the collagen fibers, is reduced in the tissue, resulting in stiffness, less ability to deform to stress, and reduced nutritional status. Changes in the vertebral column, stiff-ening of the ligaments and joints, and hardening of the tendons result in mild flexion of the vertebrae, hips, knees, elbows, wrists, and neck. With age, bone formation is slowed in relation to absorption. This results in loss of bone mass and weakening of the structure. Certain changes that occur are also a result of disuse. The loss is greater in women as the estrogen levels drop. Trabecular bone (the net-work found in the medullary cavity) loss is greater than cortical bone and areas with a higher ratio of tra-becular bone, such as the head of femur, radius, and vertebral bodies, are more prone for fractures. The production of synovial fluid in the joints de-creases with age. The articular cartilages become thinner. Because joints are also affected by genetic makeup and wear and tear, the changes observed with age vary individually. Osteoarthritis is associ-ated with increasing age. **The Skeletal System, Joints, and Massage** In general, massage therapy is not used extensively to correct bony deformities. However, problems related to tendons, bursae, and muscles around joints can be addressed. Also, the psychological benefits of touch should not be forgotten. When joints are immobilized, the connective tissue elements, such as capsules, ligaments, and surrounding tendons, tend to loose their elasticity be-cause of the release of water from the ground substance that allows connective tissue fibers to come in closer contact and form abnormal cross-linkages between them. By manipulation of joints (including joint replacements), a massage therapist can facilitate breakage of cross-linkages and increase range of motion. Range of motion can also be im-proved by regular passive and active exercises, use of special techniques to prevent adhesions, and by re-ducing spasm of surrounding muscles. Chiroprac-tors and physiotherapists specialize in the use of techniques that help mobilize joints. Massage has been shown to be of benefit to those suffering from joint-related disorders such as arthri-tis.^1^ It reduces stiffness and swelling, increases blood flow, relieves pain and muscle spasm, and mobilizes fibrous tissue.^2^ By improving muscle action, it in-duces a state of general relaxation. Ice massage or immersion, applied using specific techniques, are es-pecially helpful in pain relief and, thereby, introduc-tion of early mobilization exercises.^3^ Massage prior to mobilization is also very useful. Massage has been shown to benefit those with some types of low back pain by decreasing pain and associated depression and anxiety and by increasing range of motion.^4-9^ However, a 1999 review^6^ of stud-ies in which massage was used for low back pain con-cluded that there is inadequate evidence; that mas-sage has some potential as a therapy, but more reliable studies are needed. Some studies published after this review have shown improvements in range of motion.^7-10^ Massage has also been shown to improve the range of motion and performance of university dancers^11^ and the elderly.^12^A study of patients with spinal cord injuries^13^ showed improvement in range of motion and muscle function in these patients. Massage may lessen the fibrosis that usually devel-ops after injury. Friction massage has been used on muscles, ligaments, tendons, and tendon sheaths for prevention and treatment of scar tissue formation.^14^Deep transverse friction massage has been found to be particularly beneficial in conditions such as chronic tendinitis and bursitis. This technique breaks down scar tissue, increases extensibility and mobility of the structure, promotes normal orientation of col-lagen fibers, increases blood flow (thereby, speeding healing), reduces stress levels, and allows healing to take place.^14^ Although friction massage is beneficial to the underlying structures as stated above, it should be avoided if the nutritional status of the skin is com-promised in the area. Before massaging a client with musculoskeletal disorders, a therapist should obtain a thorough his-tory. Massage is contraindicated locally and generally in many musculoskeletal conditions. Acute arthritis of any type, fractures, dislocation, ruptured liga-ments, recent trauma (e.g., whiplash), severe osteo-porosis, and prolapse of intervertebral disk with nerve dysfunction are just a few of the conditions. **THE MYOFILAMENT: THE SPECIALIZED PROTEINS OF MYOFIBRILS** Each myofibril is made up of **myofilaments,** which are regular arrangements of protein filaments (Figure 4.3). Myofilaments, unlike the myofibrils, do not run the entire length of the muscle fiber, but are arranged in smaller sections called **sarcomeres.** The sarcom-ere is the functional unit (the smallest structure(s) of an organ that can perform the function) of the mus-cle, and it is the activity at the level of the sarcomere that causes muscle to contract.  Myofilaments consist of two types of protein, **actin** and **myosin.** Because of size, actin is known as the **thinfilament, **and myosin is known as the** thick filament.** The thick and thin filaments are arranged in a specific manner to facilitate muscle contraction. The filaments are arranged parallel, with bundles of thick filaments alternating with bundles of thin. When the muscle is viewed under the microscope, the thick and the thin fil-ament arrangements allow light to pass through differ-ently, and the muscle looks as if it has alternating dark (thick filaments) and light bands (thin filaments). Arrangement of Thick and Thin Filaments --------------------------------------- The thin actin filaments are arranged in such a way that they can slide between the myosin filaments (see Figure 4.3). The actin filaments are held in place by protein fibers running at right angles to the myofibril. This is known as the **Z line,** or **Z disk** (Z is an abbre-viation for zigzag). The Z disk separates one sarcom-ere from another. The myosin filaments are held in place by protein fibers that, like the Z line, run at right angles to the direction of the myofibril. This is the **Mline **(M for middle---it is in the middle of the sarcom-ere). The width of myofibril, occupied by the actin fil-aments (on either side of the Z line), is the **I band,** and the width of myofibril, occupied by the myosin fila-ments, is the **A band.** The myosin and actin filaments do not overlap at the center of the A band---the A band appears lighter and this is known as the **H zone.** Structure of Thin (Actin) Filaments ----------------------------------- The thin, actin filament consists of three types of pro-teins that play a key role in muscle contraction (Fig-ure 4.3). Actin is actually twisted strands of globular pro-teins. An analogy would be two strings of pearls twisted together. Each globular molecule has a site that has an affinity for myosin filament. These sites (**active sites** or **myosin-binding sites**) are covered by **tropomyosin, **another strand of protein. Tropomyosinin this position prevents actin-myosin interaction. A third type of protein (**troponin**) is located at reg-ular intervals on the tropomyosin. Troponin holds the tropomyosin in position. It also carries a site; how-ever, this site has an affinity for calcium. Structure of Thick (Myosin) Filaments ------------------------------------- Each thick filament consists of many (approximately 300) myosin molecules. Each myosin molecule re-sembles two hockey sticks that have the shafts wound together, with a long arm (**tail**) and an angulated base (**head).** The myosin molecules are arranged with all the heads directed outward. Therefore, the heads project toward adjacent actin molecules. All tails face the M line, so that there are some heads to the right and some to the left of the M line. The heads of the myosin molecules have a site that has an affinity for actin. Because the heads interact with the actin during contraction, they are also known as**crossbridges.** The head has the ability to move forward and backward on the tail, as if there was a hinge at the junction of the head and the tail. It is the movement of the heads that results in reduc-tion in muscle size during contraction. Other than actin and myosin, many other proteins help secure the myofilaments in place and provide the elasticity and extensibility of myofibrils. To understand this section, familiarity with the de-tailed structure of the muscle fiber is crucial. If nec-essary, review the details and the Figures. The actual process of muscle contraction can be explained by the **sliding filament theory.** **SLIDING FILAMENT MECHANISM**   The sliding filament mechanism explains the process of muscle contraction at the molecular level. This process is initiated by impulses from the nerve that innervates the muscle fiber. Muscle-Nerve Communication -------------------------- Skeletal muscle only contracts when stimulated by the communicating nerve. Each muscle fiber is in contact with a nerve ending. The cell body of the nerve fiber (a single neuron) is located in the spinal cord, brainstem, or brain, according to where the skeletal muscle is located and to where it originated in the embryonic stage. The axons of these neurons extend from the cell bodies to individual muscles.  For example, when we say that the ulna nerve sup-plies the muscles of the thumb, we are indicating the bundles of axons of motor neurons that go together as the ulna nerve before they split to supply the indi-vidual muscle fibers of muscles that move the thumb. The axons branch when they reach the muscles they supply, and each axon communicates with one or more muscle fibers. Thus, if a neuron is stimu-lated, all of the muscle fibers it communicates with will contract. The axon, its branches, and all the mus-cle fibers it supplies are known as a **motor unit** (see Figure 4.4). A motor neuron innervates an average of 150 muscle fibers. However, in muscles that require precise control, a neuron may innervate only two or three fibers. Diagram Description automatically generated At the point where they come in close contact with the muscle fiber, each nerve ending is modified. The region where the nerve and the muscle communicates is the**myoneural junction** or **neuromuscular junc-tion **(see Figure 4.5). The nerve ending expands hereto form a **synaptic knob.** The cytoplasm of the nerve ending has vesicles containing molecules of **acetyl-choline **(ACh). A small gap---**synaptic cleft**---existsbetween the synaptic knob and the sarcolemma of the muscle fiber. The portion of the sarcolemma directly under the synaptic knob is the **motor endplate.** The sarcolemma underlying the synaptic knob has proteins (**receptors**) on its surface that have an affinity for ACh.  The receptors are actually ion channels that are regulated by ACh. The connective tissue matrix in the synaptic cleft has **acetylcholinesterase** enzymes that can destroy ACh.  Nerve Impulse and Activityin the Myoneural Junction --------------------------------------------------- When a specific muscle is moved, nerve impulses or action potentials  pass down the nerve axon until the myo-neural junction is reached. This triggers opening of calcium channels in the nerve axon, with resultant movement of calcium into the axon. The calcium movement triggers vesicles containing ACh to fuse with the nerve cell membrane and release ACh into the synaptic cleft. ACh attaches to the ACh receptors on the motor endplate, resulting in opening of the ion channels in the sarcolemma. The changes produced by ACh only last for a short time because the acetyl-cholinesterase located in the synaptic cleft begins to break down ACh. The sarcolemmal properties reach that of the resting stage when all ACh is destroyed. Excitation-Contraction Coupling ------------------------------- When ACh binds to the receptor, the change that oc-curs is the opening of sodium channels on the sar-colemma. This results in sodium (which is of a higher concentration outside the cell than inside) rushing into the sarcoplasm of the muscle fiber. At rest, the in-side of the muscle fiber is electrically negative com-pared to the outside. When positively charged sodium enters the cell, the inside becomes positive. This change in potential triggers a series of reactions in-side the muscle fiber at the molecular level that pro-duces muscle contraction (see Figure 4.6). The link between the potential change in the sarcolemma and the contraction of the muscle is known as **excitation-contraction coupling.** Diagram Description automatically generated**\ ** The potential change at the sarcolemma continues down into the T tubules, directly into the muscle fiber where it triggers the sarcoplasmic reticulum to re-lease calcium into the sarcoplasm. The calcium binds to the calcium site on the troponin (the protein on the actin). This binding causes the troponin to shift the tropomyosin, exposing the active site for myosin lo-cated on actin. When exposed by the movement of tropomyosin, the myosin heads attach to the active site. The myosin head moves toward the M line in a hingelike action, deriving energy from breaking down ATP (adenosine triphosphate). ATP → ADP (adenosine diphosphate)       phosphate ADP and phosphate, the breakdown products, move away and another ATP binds to the myosin head to provide energy. The attachment of the next ATP to the myosin head causes the myosin to detach from the actin site, move back into its original position, and attach to another active site on the actin.  Thus, the actin is moved closer to the M line, with the myosin attaching and detaching from the active sites on subsequent actin molecules. This process contin- ues for as long as calcium ions are present in the sar-coplasm and ATP is available for energy. Thus, the actin filament slides between the myosin filaments, shortening the muscle fiber. Relaxation of Muscle Fiber -------------------------- Soon after the impulse arrives, the sarcoplasmic reticulum that released its calcium content into the sarcoplasm starts pumping the calcium back, using ATP as energy. If no other impulse arrives, the cal-cium continues to be pumped back from the sar-coplasm until the resting levels of calcium are reached. When the calcium level drops in the sar- coplasm, the troponin loses calcium from its binding site and the tropomyosin returns to its original posi-tion, blocking the active sites in the actin and ending the actin-myosin interaction. This results in relax-ation of the muscle. As long as action potential/impulses arrive at the myoneural junction, ACh continues to be released. As mentioned, ACh is broken down by acetylcholines-terase. If impulses stop, no additional ACh is released, and the remaining ACh in the synaptic cleft is removed by acetylcholinesterase. The sodium channels that were opened by ACh binding to receptors close, and the po-tential inside the sarcoplasm is brought back to its rest-ing state. (The details of how the potential is brought back are not elaborated here). Time Lapse Between NerveImpulse and Contraction ----------------------------------------------- The **latent period** is the short duration of time that elapses when a muscle responds to a single impulse before the muscle begins to shorten. This includes the time taken for the impulse to travel down the nerve, release ACh, and all the reactions that take place within the sarcoplasm before sliding of the fila-ments occurs. In addition, it includes the time for the tendon and other connective tissue (e.g., perimysium, epimysium) to be stretched before the force can be transmitted to the bone. Because the muscle is at-tached to the bone via the connective tissue tendon, the tendon (with its elastic fibers) must be stretched for the force produced by the muscle to reach the bone. This is similar to lifting a ball tied to an elastic band. Before the ball can be lifted off the ground, the elastic band must be tautly stretched. In the muscle, the first few impulses produce enough muscle con-traction to stretch the tendon. If impulses continue to come down the nerve, the tension is transmitted to the bone more effectively. The **contraction period** is the duration of muscle contraction in response to a nerve impulse, and the **relaxation period **is the duration taken by the fiberto relax after a contraction (see Figure 4.7). The recording of the response of the muscle to a single nerve impulse is known as a **muscle twitch.** For a short time after the first impulse arrives, the muscle is unable to respond to a second stimuli. This period is known as the **refractory period.** The refractory pe-riod in skeletal muscle is short, about 5 milliseconds (ms). As a result of the short refractory period, an-other impulse arriving just after 5 ms can produce a muscle response. Note that this impulse would arrive during the contraction period of the first muscle twitch. Therefore, it is possible for the response to the second impulse to fuse with that of the first to produce a sustained contraction.  Fortunately, the refractory period in cardiac mus-cle is long, about 300 ms. This prevents sustained contractions of the heart---a situation that would stop circulation of blood. Diagram Description automatically generated ### Ligaments The **medial ligament,** or the **deltoid ligament,** is a thickening of the medial fibrous capsule that attaches the medial malleolus to the navicular, calcaneus, and talus bones. The **calcaneofibular ligament** extends from the lateral malleolus to the calcaneus. Anteri-orly and posteriorly, ligaments extend from the lat-eral malleolus to the talus to form the **anteriortalofibular **(most frequently injured) and** posterior talofibular ligaments. **The various ligaments pre-vent tilt and rotation of the talus and forward and backward movement of the leg over the talus. ### Possible Movements The ankle allows dorsiflexion and plantar flexion. However, the subtalar joint and tarsal joints allow further movement. Eversion and inversion is possible at the subtalar joint. The foot can be adducted and abducted at the midtarsal joints. The metatarsopha-langeal joints and interphalangeal joints are hinge joints, allowing flexion and extension of the toes. ### Range of Motion Dorsiflexion, 20° Plantar flexion, 50° Inversion and eversion, 5° Adduction, 20° Abduction, 10° Flexion (toes), 45° Extension, 70--90° ### Muscles Muscles that cause plantar flexion: *Primary plantar flexors* Gastrocnemius Soleus *Secondary plantar flexors* Tibialis posterior Flexors of the toes Peroneus longus and brevis Muscles that cause dorsiflexion: Tibialis anterior Peroneus tertius Extensors of the toes Muscle that inverts the foot: Tibialis anterior and posterior Muscle that everts the foot: Peroneus longus, brevis, and tertius ### Physical Assessment #### Inspection The external appearance of the shoe and foot should provide information. The alignment of the toes and the shape of the foot and arches should be inspected. The color of the skin and presence of swelling should also be noted. #### Palpation The bones of the foot and ankle are easily palpated. Some bony prominences that can be located are the malleoli, talus, calcaneus, and the metatarsal and phalanges. The deltoid ligament is also palpable infe-rior to the medial malleolus. The long saphenous vein, if dilated may be visible just anterior to the me-dial malleolus. Both active and passive range of mo-tion should be tested at the various joints. ARCHES OF THE FOOT ------------------ The foot has three major arches that help distribute the weight of the body between the heel and the ball of the foot during standing and walking. Two longitudi-nal---the**medial** and the **lateral longitudinal arch**--- and one transverse---the **transverse arch**---exist. The shape of the arch is maintained by ligaments, the ten-dons attached to the foot, and the configuration of the bones. The medial arch is formed by the calcaneus, talus, navicular, cuneiforms and the medial three metatarsal bones. The lateral arch is formed by the calcaneus, cuboid, and the two lateral metatarsals. The transverse arch is formed by the cuboid and cuneiform bones. **SACROILIAC JOINT** In osteopathic medicine, the sacroiliac joint is con-sidered as two joints---the sacroiliac joint (where the sacrum moves in relation to the ilium) and iliosacral joint (where the ilium moves in relation to the sacrum). This is so because the sacrum is associated with the spine and helps transmit forces from above to the pelvis, and the ilium is closely associated with the lower limb and transmits forces upwards. Articulating Surfaces and Type of Joint --------------------------------------- The two synovial joints between the medial surface of the ilium and the lateral aspect of the upper sacral vertebrae are L-shaped when viewed laterally. The ar-ticular surfaces are covered with cartilage and marked by elevations and depressions that fit each other and make the joint stronger. Ligaments --------- The ligaments that bind the sacrum to the ilium withstand the major forces through the sacroiliac joints. They form a network of fibrous bands. Many ligaments---**iliolumbar, sacrolumbar, sacroiliac** (an-terior and posterior), **sacrotuberous** (sacrum to is-chial tuberosity), and **sacrospinous**---are found around the joints (Figure 3.44). Of these, the iliolum-bar, which extends from the transverse process of the 5th vertebrae to the posterior iliac crest, is the most important as it stabilizes the 5th vertebrae on the sacrum. In addition, the muscles adjacent to the joint---gluteus maximus, gluteus minimus, piriformis, latissimus dorsi, quadratus lumborum, and iliacus--- have fibrous attachments that blend with the liga-ments and make the joints even stronger.  Possible Movements and Range of Motion -------------------------------------- The movements of this joint are limited, but even this limited movement is important. The main function of this joint is to serve as a shock absorber. The move-ment of the sacrum is described as flexion (nutation) and extension (counter-nutation). During flexion the sacral promontory moves anteriorly and inferiorly with the apex moving posteriorly, while the iliac bones approximate and the ischial tuberosities move apart. Such a movement occurs when walking and when bending forward (flexion) and backward (exten-sion). During walking, the movement of the sacrum is determined by the forces from above, while the move-ment of the ilium is determined by the femur. Muscles ------- Though this joint is surrounded by strong muscles, none play a direct part in moving the sacrum. Sacral movement is a result of the pull of forces through lig-aments and gravity. By pulling on the ilia, the muscles in the vicinity have an indirect effect on the sacrum. There are 35 muscles attached to the sacrum or hipbones and, together with the ligaments and fascia, they help coordinate movement of the trunk and lower limbs. Problems associated with any of them can result in alteration of the mechanics of the pelvis. The quadratus lumborum, erector spinae, abdominal muscles, rectus femoris, iliopsoas, tensor fascia latae, piriformis, short hip adductors, hamstrings, gluteus maximus, medius and minimus, vastus medialis and lateralis, the pelvic floor muscles are important mus-cles that must be considered in a client with low back pain. Physical Assessment ------------------- When assessing this joint, it is important to take a good history that includes history of trauma and ab-normal stress to the region. Typically, the pain arising from this joint is unilateral, increased by walking, get-ting off the bed, and climbing stairs, etc. Examination of this joint should be done in conjunction with the hip joint and lumbar spine as the pain may be re-ferred to this joint from those areas. Description of in-dividual tests used for assessing this joint is beyond the scope of the book. The gait, posture, alignment of bony structures, difference in leg length, and passive and active movements should be tested, and treat-ment aimed at normalizing the stresses on the lum-bopelvic complex should be based on the findings. **SLIDING FILAMENT MECHANISM**   The sliding filament mechanism explains the process of muscle contraction at the molecular level. This process is initiated by impulses from the nerve that innervates the muscle fiber. Muscle-Nerve Communication -------------------------- Skeletal muscle only contracts when stimulated by the communicating nerve. Each muscle fiber is in contact with a nerve ending. The cell body of the nerve fiber (a single neuron) is located in the spinal cord, brainstem, or brain, according to where the skeletal muscle is located and to whe