joints.docx

Define the term articulation, and discuss the two major classification systems for joints. Articulation - joints - point of contact between bone and bone or bone and cartilage or bone and teeth Their function is to provide mobility and stability and also hold skeleton together. There are two classi...

Define the term articulation, and discuss the two major classification systems for joints. Articulation - joints - point of contact between bone and bone or bone and cartilage or bone and teeth Their function is to provide mobility and stability and also hold skeleton together. There are two classification systems: Structural: based on the material that binds the joints/ connecting tissue and whether there is a synovial cavity or not Fibrous – connected by fibrous connective tissue Cartilaginous – connected by fibrocartilage or hyaline cartilage Depending on their location, they can be classified functionally as either synarthroses or amphiarthroses Synovial – connect and articulate with each other within a joint cavity filled with synovial fluid - diarthroses synovial fluid, provide lubrication, nutrients and also allow free movement between the bones. within these joints the articulating surfaces are not directly held by any other tissues to each other but come into contact within a fluid filled cavity Functional: degree of movement the joint is capable of Synarthroses – immovable Amphiarthroses – slightly movable Diarthroses – freely movable – only synovial joints The amount of movement at any joint is determined by their functions. Immobile and slightly movable joints help to protect internal organs, provide stability to body and enable limited movement. But freely movable joints allow bodily and limb movements. Compare and contrast the terms synarthroses, amphiarthroses, and diarthroses. Joints can be synarthroses (immovable), amphiarthroses (partially movable), or diarthroses (freely movable). The joints are also classified based on the degree and amount of mobility that is possible between the adjacent bones. Synarthrosis: immobile/ immovable joint - this allows for a strong union between the articulating bones - important for protecting internal organs - corneal sutures are synarthrosis fibrous joints between the bones that make up the skull, covering and protecting the brain. Suture Joints of Skull. These are examples of synarthroses, essentially immobile joints in adults Amphiarthrosis: slightly movable joints - a layer of cartilage or longer fiber allow limited mobility while holding the articulating surfaces tightly to each other - intervertebral discs are thick layers of fibrocartilage that fills the gap between the vertebrae and strongly hold them together while still providing a limited amount of movement between them - these small movements can then sum together along the vertebrae to allow larger ranges of body movement - so intervertebral discs are cartilaginous amphiarthrosis types of joints. Intervertebral Disc. An intervertebral discunites the bodies of adjacent vertebrae. These discs are functional amphiarthroses, and are composed of fibrocartilage, forming a symphysis type of cartilaginous joint. Diarthrosis: freely movable joints - all synovial joints of the body that provide the majority of body movements - most found in the appendicular skeleton so they allow limbs to have a wide range of motion. Based on number of the axes of motion in the three anatomical planes that they provide, they are divided into three categories: Uniaxial joints: allow for movement in only one single anatomical plane - elbow joint only allows for bending or straightening Biaxial joints: allow for movement and motion within two anatomical planes - knuckle joints which allow movement along one plane or axis to produce bending or straightening of finger plus they allow movement along a second plane or axis which allow fingers to be spread away from each other or brought back together. Multiaxial/ polyaxia l/ triaxial joints: movement in all three anatomical planes (sagittal, transverse, frontal) so able to moved in several directions - shoulder and hip joints - anterior-posterior, medial-lateral, and rotational along the long axis Multiaxial Joint. A multiaxial joint like the hip joint is a functional diarthrosis, allowing free movement in all three planes: transverse, frontal, and sagittal Name the three types of fibrous joints, and give an example of each. Fibrous joints: adjacent bones are directly held and connected to each other by fibrous connective tissues. The gaps between them could be wide or narrow but there is no synovial cavity between them. The connective tissues allow little or no movement at these joints. 3 types: Suture: narrow and synarthrosis fibrous joints made of thin layer of dense and fibrous connective tissue that fills all gaps and connects all bones of skull strongly together except the mandible. By holding the skull bones intensely united they help protect the brain and form the face. Some sutures may allow slight movements between the cranial bones. A synostosis is a suture joint that has ossified. An example of a synostosis is the frontal suture between the left and right sides of the frontal bone. Fontanelles are areas of connective tissue on the skull that provide flexibility and allow for the growth of the skull and enlargement of the brain. During birth, they enable the infant's head to pass through the birth canal, and after birth, they provide for rapid growth of the skull and brain. Over time, the fontanelles gradually decrease in width and the connective tissue between the adjacent bones may ossify and be converted into bone, forming a synostosis. Synostosis fusions between cranial bones can occur both early and late in life. At birth, the frontal and maxillary bones are two distinct halves connected by sutures, which dissolve over time. By the age of eight, these bones are fused together into one piece. As individuals age, the sagittal, coronal and lambdoid sutures of the skull also gradually ossify and fuse, making the suture lines become less and less visible. Syndesmoses: bones are connected using more fibrous connective tissue between the bones than in suture. Interosseous membranes are sheets of dense irregular connective tissue that hold two long bones united to each other by more fibrous connective tissues than in the sutures and prevent their separation. These provide some amount of movement so they are classified as amphiarthrosis. In leg, they strongly hold the bones together and allow limited movement in order to provide strength, stability and ability to bear weight. In forearms, the interosseous membrane provides some flexibility to allow greater motion. If the gap between the bones is narrow - they are joined by ligaments If the gap between the bones is wide - gap is filled with a sheet of dense irregular connective tissue known as interosseous membrane and these join long bones such as radius and ulna Interosseous membrane: sheet of dense irregular connective tissue uniting two long bones. These membranes not only hold the parallel bones, provide strength, stability and some flexibility, but they also provide points of attachments for muscles. Gomphosis: A gomphosis is a type of joint that connects a tooth to the bone in the upper or lower jaw. It is also known as a peg-and-socket joint. The joint is composed of a number of bands of connective tissue, called periodontal ligaments, which secure the tooth in its socket and prevent movement. This type of joint is immobile and is therefore classified as synarthrosis. Fibrous Joints. Fibrous joints form strong connections between bones. (a) Sutures join most bones of the skull. (b) An interosseus membrane forms a syndesmosis between the radius and ulna bones of the forearm. (c) A gomphosis is a specialized fibrous joint that anchors a tooth to its socket in the jaw. Name the two types of cartilaginous joints. Cartilaginous joints are the ones that the articulating bones are united by either hyaline cartilage or fibrocartilage which are both tough connective tissues and allow little or no movement at all. These also lack the synovial cavity. The two types of cartilaginous joints are: Synchondroses: synarthrosis cartilaginous joints in which bones are connected to each other by a hyaline cartilage or a bone is just connected to a hyaline cartilage - no movement Can be permanent such as the ones in thoracic cage where ribs are joined together and hyaline cartilage do not get ossified Can be temporary such as the epiphyseal plate that connects the diaphysis and epiphysis of long bones but overtime the hyaline cartilage gets replaced by bone and the diaphysis and epiphysis fuse together and form a single adult bone Symphyses: amphiarthrosis cartilaginous joints where bones are connected by a disc of fibrocartilage. Fibrocartilage is strong due to thick bundles of collagen fibers - so greater ability to resist pulling and bending forces than the hyaline cartilage so some limited movements can occur within the strongly united adjacent bones Pubic symphysis - right and left hip bones of pelvis are strongly united together by fibrocartilage through a narrow gap Intervertebral symphysis - thick layers of fibrocartilage known as intervertebral discs that hold the vertebrae together and fills the wide gaps between them - thicker symphysis provides cushioning and allows some motion between the adjacent vertebra Cartilaginous Joints. At cartilaginous joints, bones are united by hyaline cartilage to form a synchondrosis, or by fibrocartilage to form a symphysis. (a) The hyaline cartilage of the epiphyseal plate (growth plate) forms a synchondrosis that unites the shaft (diaphysis) and end (epiphysis) of a long bone and allows the bone to grow in length. (b) The pubic portions of the right and left hip bones of the pelvis are joined together by fibrocartilage, forming the pubic symphysis. Describe a typical synovial joint. Synovial joints: Bones are separated by fluid filled synovial/ joint cavity: Instead of directly being connected with another tissues, these joints have a fluid filled cavity (synovial cavity) at which the surfaces of the articulating bones contact each other. This characteristic allows them to move freely against each other and be more mobile All are diarthrotic and freely movable All limb joints are of this kind They all have 6 general features: Articular cartilage: hyaline cartilage covers the ends of the bones to reduce friction and also absorb shock and prevent crushing of bone ends Synovial cavity: small fluid filled space – synovial fluid: mostly water and hyaluronic acid – viscous and provide lubrication + nutrients Articular/ joint capsule: surrounds and encases the synovial cavity and has two layers: External fibrous layer: dense irregular connective tissue and may contain ligaments Inner synovial membrane: lines the inner surfaces of synovial joint - loose aerolar connective tissue that makes the synovial fluid – lubrication and nourishment Flexibility of the fibrous capsule is flexible which allow joints to have considerable movements and at the same time it has a great tensile strength which and prevents bones from getting dislocated Synovial fluid: viscous and slippery fluid that: Secreted by the synovial membrane Lubricates and reduces friction Provides nutrients and removes metabolic wastes Different types of reinforcing ligaments: Ligaments support the joint by holding bones to bones and resisting excess or abnormal joint motions. Capsular: thickened part of the fibrous layer of articular capsule Extracapsular: outside the capsule – support the joint from the outside Intracapsular: found within the joint itself and are deep to capsule; they are covered with synovial membrane Nerves and blood vessels Nerves supplying the joints are the same ones that supply the skeletal muscles moving that joint and they detect pain and monitor joint position and stretch Capillary beds to nourish synovial membrane and supply plasma to make synovial fluid Other features of synovial joints: At many synovial joints, additional support is provided by the muscles and their tendons that act across the joint. A tendon is the dense connective tissue structure that attaches a muscle to bone. As forces acting on a joint increase, the body will automatically increase the overall strength of contraction of the muscles crossing that joint, thus allowing the muscle and its tendon to serve as a “dynamic ligament” to resist forces and support the joint. This type of indirect support by muscles is very important at the shoulder joint, for example, where the ligaments are relatively weak. Fatty pads: within synovial joints - provide cushioning and reduce friction to provide cushioning between the fibrous layer of capsule and synovial membrane or bone Articular discs/ menisci: fibrocartilage separating the articular surfaces and the modify the shape of surfaces of the bones articulating together and give them a better fit, help in maintaining the stability of joints, and they also direct the flow of synovial fluid to areas that have higher friction therefore reducing the wear and tear- mostly in places that endure a lot of weight - knees If they are round and oval the are called articular disc If they are larger and C shaped they are called meniscus Depending on the joint, these have different functions. In some places, articular disc strongly unite the bones of the joint for example articular discs between distal ends of radius and ulna Meniscus within the knee joint, provide shock absorption and cushioning between the bones Some articular discs smooth the movements between the articulating bones Have bursae and tendon sheaths associated with them Bursae: a thin connective tissue sac that is filled with a lubricating fluid and is located outside of the synovial joints in regions where there is a skin, ligament, muscle or muscle tendon overlying the bones of the joint and their function is to separate the neighbouring structures and reduce the friction between them by preventing them to rub directly against each other. There are three types of them based on their location: Subcutaneous bursa: these are located between the skin and the bone that is underneath them allowing the skin to move smoothly over the bone. For example: prepatellar bursa located over the kneecap and the olecranon bursa at the tip of the elbow. Submuscular bursa: found between muscle and its underlying bone or between adjacent muscles. These sacs prevent muscles from rubbing against each other during movements. For example, . A large submuscular bursa, the trochanteric bursa, is found at the lateral hip, between the greater trochanter of the femur and the overlying gluteus maximus muscle. Subtendinous bursa: is a sac that is found between a tendon and a bone. For example, the subacromial bursa that protects the tendon of shoulder muscle as it passes under the acromion of the scapula, and the suprapatellar bursa that separates the tendon of the large anterior thigh muscle from the distal femur just above the knee. Tendon Sheats: some joints also have tendon sheats which are also connective tissue sacs containing lubricating fluids like bursa. These surround the muscle tendons in regions where they cross joints and are subjected to friction. These allow the smooth motion of tendons during muscle contraction and joint movements by reducing the friction between them. A few synovial joints of the body have a fibrocartilage structure located between the articulating bones. This is called an articular disc, which is generally small and oval-shaped, or a meniscus, which is larger and C-shaped. These structures can serve several functions, depending on the specific joint. In some places, an articular disc may act to strongly unite the bones of the joint to each other. Examples of this include the articular discs found at the sternoclavicular joint or between the distal ends of the radius and ulna bones. At other synovial joints, the disc can provide shock absorption and cushioning between the bones, which is the function of each meniscus within the knee joint. Finally, an articular disc can serve to smooth the movements between the articulating bones, as seen at the temporomandibular joint. Some synovial joints also have a fat pad, which can serve as a cushion between the bones. Additional structures located outside of a synovial joint serve to prevent friction between the bones of the joint and the overlying muscle tendons or skin. A bursa (plural = bursae) is a thin connective tissue sac filled with lubricating liquid. They are located in regions where skin, ligaments, muscles, or muscle tendons can rub against each other, usually near a body joint Bursae reduce friction by separating the adjacent structures, preventing them from rubbing directly against each other. Bursae are classified by their location. A subcutaneous bursa is located between the skin and an underlying bone. It allows skin to move smoothly over the bone. Examples include the prepatellar bursa located over the kneecap and the olecranon bursa at the tip of the elbow. A submuscular bursa is found between a muscle and an underlying bone, or between adjacent muscles. These prevent rubbing of the muscle during movements. A large submuscular bursa, the trochanteric bursa, is found at the lateral hip, between the greater trochanter of the femur and the overlying gluteus maximus muscle. A subtendinous bursa is found between a tendon and a bone. Examples include the subacromial bursa that protects the tendon of shoulder muscle as it passes under the acromion of the scapula, and the suprapatellar bursa that separates the tendon of the large anterior thigh muscle from the distal femur just above the knee. A tendon sheath is similar in structure to a bursa, but smaller. It is a connective tissue sac that surrounds a muscle tendon at places where the tendon crosses a joint. It contains a lubricating fluid that allows for smooth motions of the tendon during muscle contraction and joint movements. Synovial Joints. Synovial joints allow for smooth movements between adjacent bones. The joint is surrounded by an articular capsule that defines a joint cavity filled with synovial fluid. The articulating surfaces of the bones are covered by a thin layer of articular cartilage. Ligaments support the joint by holding the bones together and resisting excess or abnormal joint motions Bursae. Bursae are fluid-filled sacs that prevent friction between skin, muscle, or tendon and an underlying bone. Three bursae and a fat pad are part of the complex joint that unites the femur and tibia at the knee. Describe the structure and function of the knee joint - largest joint of the body Knee Joint.The knee joint is the largest in the body and is supported by the tibial and fibular collateral ligaments outside of the articular capsule, and the anterior and posterior cruciate ligaments found inside the capsule. The medial and lateral menisci provide padding and support between the femoral condyles and tibial condyles Knee joint: Complex hinge joint, largest joint in body Allowing flexion and extension of leg This action of flexion and extension is generated by both gliding and rolling motion of femur on the tibia Some rotation of leg is also available only when the leg is flexed Knee is constructed in a way to bear weight when it is in extended position but is vulnerable to injuries associated with hyperextension, twisting, or blows to the medial or lateral side of the joint, particularly while weight bearing (extended position) Knee joint structure: knee joint has three articulations all enclosed within a single articular/ joint capsule: Femoropatellar joint - found between patella and distal femur - At this joint, the patella slides vertically within a groove on the distal femur Lateral tibiofemoral joint - between lateral condyles of femur and lateral condyle of tibia Medial tibiofemoral joint - between the medial condyles of femur and medial condyle of tibia Tibiofemoral joints: The medial and lateral tibiofemoral joints are the articulations between the rounded condyles of the femur and the relatively flat condyles of the tibia. During flexion and extension motions, the condyles of the femur both roll and glide over the surfaces of the tibia The rolling action produces flexion or extension gliding action serves to maintain the femoral condyles centered over the tibial condyles, thus ensuring maximal bony, weight-bearing support for the femur in all knee positions. As the knee comes into full extension, the femur undergoes a slight medial rotation in relation to tibia. The rotation results because the lateral condyle of the femur is slightly smaller than the medial condyle. Thus, the lateral condyle finishes its rolling motion first, followed by the medial condyle. The resulting small medial rotation of the femur serves to “lock” the knee into its fully extended and most stable position Flexion of the knee is initiated by a slight lateral rotation of the femur on the tibia, which “unlocks” the knee. This lateral rotation motion is produced by the popliteus muscle of the posterior leg. Patella: sesamoid bone incorporated into the tendon of the quadriceps femoris muscle, the large muscle of the anterior thigh serves to protect the quadriceps tendon from friction against the distal femur as well compressive forces Continuing from the patella to the anterior tibia just below the knee is the patellar ligament. Acting via the patella and patellar ligament, the quadriceps femoris is a powerful muscle that acts to extend the leg at the knee Patellar ligament also serves as a “dynamic ligament” to provide very important support and stabilization for the knee joint. Meniscus: C-shaped fibrocartilage structure that is thin along its inside margin and thick along the outer margin. Located between the articulating surfaces of the femur and tibia are two articular discs, the medial meniscus and lateral meniscus They are attached to their tibial condyles, but do not attach to the femur. While both menisci are free to move during knee motions, the medial meniscus shows less movement because it is anchored at its outer margin to the articular capsule and tibial collateral ligament. The menisci provide padding between the bones and help to fill the gap between the round femoral condyles and flattened tibial condyle Some areas of each meniscus lack an arterial blood supply and thus these areas heal poorly if damaged. Ligaments: The knee joint has multiple ligaments that provide support, particularly in the extended position Outside of the articular capsule, located at the sides of the knee, are two extrinsic ligaments. The fibular collateral ligament (lateral collateral ligament) is on the lateral side and spans from the lateral epicondyle of the femur to the head of the fibula. The tibial collateral ligament (medial collateral ligament) of the medial knee runs from the medial epicondyle of the femur to the medial tibia. As it crosses the knee, the tibial collateral ligament is firmly attached on its deep side to the articular capsule and to the medial meniscus, an important factor when considering knee injuries. In the fully extended knee position, both collateral ligaments are taut (tight), thus serving to stabilize and support the extended knee and preventing side-to-side or rotational motions between the femur and tibia. The articular capsule of the posterior knee is thickened by intrinsic ligaments that help to resist knee hyperextension. Inside the knee are two intracapsular ligaments: From their bottom these ligaments are anchored to tibia at the intercondylar eminence, the roughened area between the tibial condyles. The cruciate ligaments are named for whether they are attached anteriorly or posteriorly to this tibial region. Each ligament runs diagonally upward to attach to the inner aspect of a femoral condyle. Each ligament runs diagonally upward to attach to the inner aspect of a femoral condyle. the anterior cruciate ligament: becomes tight when the knee is extended, and thus resists hyperextension. posterior cruciate ligament : stronger ligament. It serves to support the knee when it is flexed and weight bearing, as when walking downhill. In this position, the posterior cruciate ligament prevents the femur from sliding anteriorly off the top of the tibia. List the types of movements allowed by synovial joints, and give examples of each. Joints allow several types of movements - Synovial joints give the body many ways in which to move. Also based on number of the axes of motion in the three anatomical planes that they provide, they are divided into three categories: Uniaxial joints: allow for movement in only one single anatomical plane - elbow joint only allows for bending or straightening Biaxial joints: allow for movement and motion within two anatomical planes - knuckle joints which allow movement along one plane or axis to produce bending or straightening of finger plus they allow movement along a second plane or axis which allow fingers to be spread away from each other or brought back together. Multiaxial/ polyaxia l/ triaxial joints: movement in all three anatomical planes (sagittal, transverse, frontal) so able to moved in several directions - shoulder and hip joints - anterior-posterior, medial-lateral, and rotational along the long axis Movements at synovial joints are grouped into the following four categories: Gliding movements occur when relatively flat bone surfaces move back and forth, and from side to side with respect to one another – for example: intercarpal joints Angular movements involve an increase or a decrease in the angle between articulating bones, and can include: Flexion and Extension: within sagittal plane and involves anterior or posterior movements of neck, trunk or limbs. These movements take place at the shoulder, hip, elbow, knee, wrist, metacarpophalangeal, metatarsophalangeal, and interphalangeal joints. Flexion: decreases the angle between the bones – anterior motions of upper limbs for example arm at the shoulder and in the lower limbs, bringing thigh forward and upward are flexion at the hip joint. Also anterior bending of head or vertebral column is considered flexion Extension: increases the angle between bones – all posterior motions of upper limbs as well as all posterior motions of the thigh - Any motion posteriorly or posterior going movement is extension Hyperextension: excessive extension of a joint beyond its normal range of motion which can result in injury Abduction and Adduction: movement within frontal also known as coronal plane and involves motions limbs, hand, fingers, toes or thumb in medial- lateral plane of movement Adduction/abduction and circumduction take place at the shoulder, hip, wrist, metacarpophalangeal, and metatarsophalangeal joints Abduction: moving limbs laterally away from the midline of the body as well as spreading the fingers or toes - raising the arm at the shoulder joint, moving it laterally away from the body Adduction: moving limbs towards the body or the midline as well as bringing fingers or toes together - bringing the arm down to the side of the body Circumduction: movement of a region of body such as limb, hand or fingers in a circular pattern using the sequential combination of flexion, adduction, extension, and abduction motions - . Rotational movement: involves a motion of the bone revolving around its own longitudinal axis or a fixed point/ axis. Rotation can occur within the vertebral column, at a pivot joint, or at a ball-and-socket joint. Turning the head side to side or twisting of the body are considered rotational movements. twisting of the body is rotation. Rotation of the neck or body is the twisting movement produced by the summation of the small rotational movements available between adjacent vertebrae. rotation of the upper limb at the shoulder or lower limb at the hip involves: Medial rotation: turning the anterior surface of the limb towards the midline of the body – medial or internal rotation Lateral rotation: turning the anterior surface of the limb away from the midline of the body - lateral or external rotation Special movement that occurs only at certain joints. Movements of the Body, Synovial joints give the body many ways in which to move. Flexion and extension are in the sagittal plane of motion. Any motion posteriorly is an extension. Abduction and adduction are in the frontal (coronal) plane. Moving a limb laterally away from the midline of the body is abduction; moving toward the midline is adduction. Circumduction is the movement of a limb, hand, or fingers in a circular pattern, using the sequential combination of flexion, adduction, extension, and abduction. Turning the head side to side or twisting of the body is rotation. Medial and lateral rotation are turns of the anterior surface of a limb toward or away from the midline of the body, respectively. List the special movements that can occur at some joints. Special movements that can occur in certain joints in the anatomical position, include the following: Elevation is an upward movement of a part of the body. Depression is a downward movement of a part of the body. Protraction is a movement of a part of the body anteriorly in the transverse plane. Retraction is a movement of a protracted part back to the anatomical position. Inversion is movement of the soles medially at the intertarsal joints so that they face each other. Eversion is a movement of the soles laterally at the intertarsal joints so that they face away from each other. Dorsiflexion refers to bending of the foot at the ankle in the direction of the superior surface. Plantar flexion involves the bending of the foot at the ankle joint in the direction of the plantar surface. Supination is a movement of the forearm at the proximal and distal radioulnar joints in which the palm is turned anteriorly or superiorly. Pronation is a movement of the forearm at the proximal and distal radioulnar joints in which the distal end of the radius crosses over the distal end of the ulna, and the palm is turned posteriorly or inferiorly. A sprain is the forcible wrenching or twisting of a joint that stretches or tears its ligaments but does not dislocate the bone. A strain is a stretched or partially torn muscle. Body Movements, Part 2. In the anatomical position, supination laterally rotates the distal end of the forearm such that the palm faces anteriorly, while pronation medially rotates the palm posteriorly. Dorsiflexion of the foot points the toes superiorly, while plantar flexion points the toes inferiorly. Eversion moves the sole of the foot away from the body’s midline, while inversion turns the sole toward the midline. Mandibular protraction pushes the chin anteriorly, and retraction moves the chin posteriorly. Depression of the mandible opens the mouth, while elevation closes it. Opposition brings the tip of the thumb into contact with the tips of the fingers of the same hand, and reposition brings the thumb back to its anatomical position next to the index finger. Movements of the Body, Part 2  Supination of the forearm turns the hand to the palm forward position in which the radius and ulna are parallel, while forearm pronation turns the hand to the palm backward position in which the radius crosses over the ulna to form an "X." Dorsiflexion of the foot at the ankle joint moves the top of the foot toward the leg, while plantar flexion lifts the heel and points the toes. Eversion of the foot moves the bottom (sole) of the foot away from the midline of the body, while foot inversion faces the sole toward the midline. Protraction of the mandible pushes the chin forward, and retraction pulls the chin back. Depression of the mandible opens the mouth, while elevation closes it. Opposition of the thumb brings the tip of the thumb into contact with the tip of the fingers of the same hand and reposition brings the thumb back next to the index finger. Describe the six subtypes of synovial joints - divided based on the shapes of the articulating surfaces of the bones forming the joints Synovial joints are classified into 6 types based on: Shape of the articulating surfaces of bones involved Types of movements they allow Synovial joints include the following six subtypes: Planar joints permit mainly side-to-side and back-and-forth gliding movements - such as those between the tarsal bones of the foot, allow for limited gliding movements between bones In a hinge joint, the convex surface of one bone fits into a concave surface of another bone - The hinge joint of the elbow works like a door hinge In a pivot joint, a round or pointed surface of one bone fits into a ring formed by another bone and a ligament - such as between the first and second cervical vertebrae, which allows for side-to-side rotation of the head In an ellipsoidal joint also known as condyloid joint, an oval-shaped condyle of one bone fits into an elliptical cavity of another bone. - The radiocarpal joint of the wrist - between radius and carpal bones of wrist A saddle joint includes one bone whose articular surface is saddle-shaped, and another bone whose articular surface is shaped like a rider sitting in the saddle - articulation between the trapezium and the first metacarpal at the base of the thumb In a ball-and-socket joint, the ball-shaped surface of one bone fits into the cuplike depression of another. - hip and shoulder joints are the only ball-and-socket joints in the body Types of Synovial Joints. Pivot joints allow for rotation around an axis, such as between the first and second cervical vertebrae, which allows for side-to-side rotation of the head. The hinge joint of the elbow works like a door hinge. The articulation between the trapezium and the first metacarpal at the base of the thumb is a saddle joint. Plane joints, such as those between the tarsal bones of the foot, allow for limited gliding movements between bones. The radiocarpal joint of the wrist is a condyloid joint. The hip and shoulder joints are the only ball-and-socket joints in the body.