Biomech Midterm Study Guide PDF
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This document is a biomechanics study guide covering topics such as the importance of the patella to the quadriceps, joints and degrees of freedom, active and passive insufficiency, muscle fiber architecture, Newton's Laws, and arthrokinematic movement. It is suitable for undergraduate students interested in biomechanics and human anatomy.
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Biomech midterm study guide 1. The importance of the patella to the quadriceps a. Pulley i. Used in the body to alter the line of pull & toadd mechanical advantageto a musculotendinous unit...
Biomech midterm study guide 1. The importance of the patella to the quadriceps a. Pulley i. Used in the body to alter the line of pull & toadd mechanical advantageto a musculotendinous unit 1. Typically by using bony prominences or ligamentous structures ii. Fixed pulley 1. Applied force is equal in each strand iii. Movable pulley 1. May change direction & magnitude of the force iv. The sesamoid bones in the patella provide the quadriceps tendon with a better line of pull 1. This is an example of the primary use of a pulley a. The primary use of a pulley i. Boostmechanical advantageby increasing the moment arm ii. Occasionally, they are used topreserve functional esthetics 1. ex) toe extensors are held by the extensor retinaculum b. Patellofemoral joint reaction force in the closed chain i. When the knee is flexed to 15° maximum, isometric quadriceps contraction is around 0.8x body weight ii. The force is increased to 2.6x body weight when the knee is at a 90° angle 2. Joints and degrees of freedom a. Degrees of freedom i. The number of planes in or around which motion takes place about the X, Y, and Z axes 1. Aka, "The number of directions in which movement happens around the X, Y, and Z axes” ii. Most commonly used are the sagittal, coronal (frontal) & transverse planes b. 1° of freedom i. Movement in only one plane ii. ex) flexion at the knees or elbows c. 2° of freedom i. Movement in two planes ii. ex) flexion/extension & adduction/abduction at the MPJ d. 3° of freedom i. Movement in three planes ii. ex) circumduction at the femoral hip joint 3. Active Insufficiency a. Muscle is weakly working at a portion of the length-tension curve that is not optimal b. The muscle is working above or below the resting length c. Examples i. Biceps contracting while in full shoulder & elbow flexion along with full forearm supination ii. Gastroc contracting while in full knee flexion & ankle PF iii. Hamstrings contracting while in full hip extension & knee flexion d. ChatGPT explanation (When a Muscle Can’t Contract Effectively) i. Active insufficiencyoccurs when amuscle is shortened too muchand can no longer generate effective force. This happens inbiarticular (two-joint) muscles, which cross two joints and perform actions at both. e. Passive insufficiencyof muscle i. Occurs in multi-joint muscles where the length of the antagonist muscle of the stretched muscle group is not sufficient to permit full elongation over all joints simultaneously ii. Example 1. The hip can be flexed to approx. 125° with a flexed knee. However, when the knee is kept in extension, hip flexion is limited to 70° b/c of passive insufficiency of the hamstrings iii. ChatGPT explanation (When a Muscle Can’t Stretch Enough) 1. Passive insufficiencyoccurs when abiarticular (two-joint) muscle is stretched too much across both joints, limiting movement because the muscle cannot lengthen further. f. Wrist grip example of active & passive insufficiency i. The maximum grip strength is greatest when the wrist is slightly extended ii. When the wrist is flexed → the grip strength is reduced iii. The ineffectual grip produced when the wrist is held in full flexion is due to the combination of active insufficiency of the long finger flexors + passive insufficiency of the antagonistic finger extensor 4. Description and characteristics of lever systems (Type 1,2, and 3) a. Class I i. Has a central axis (ex. seesaw) b. Class II i. Has a central weight (ex. wheelbarrow) c. Class III i. Has a central force d. Designated based on: i. The relative position of the motive force & resistance force acting on the lever to the fulcrum ii. Motive force (effort) 1. The force to move the lever in the desired direction a. Muscle contraction b. Class I: Neck muscle c. Class II: calf muscle d. Class III: biceps muscle iii. Resistance force (load) 1. The force in the opposite direction to the motive force a. Body weight, external object, gravity b. Class I: The weight of the head c. Class II: body weight d. Class III: weight of the forearm or dumbbell e. Class I detail i. Motive (effort) & resistance (load) are onoppositesides of the fulcrum ii. Person on the left is applying 600 N of force & sitting only 1m away from the fulcrum while the other is applying 300 N of force & sitting 2m away from the fulcrum iii. Examples 1. Atlanto-occipital joint 2. Triceps acting on elbow 3. Hip abductors in single-leg weight-bearing 4. Hamstrings & glutes counter-balancing the weight of the trunk over the hip joint axis f. Class II detail i. Motive (effort) & resistance (load) forces are on thesameside of the fulcrum ii. Themotive forcealways has the longer lever& therefore has the mechanical advantage iii. Examples 1. Wheelbarrow 2. Toe raises with the fulcrum at MPJs 3. Brachioradialis or wrist extensors maintaining elbow flexion g. Class III detail i. Motive (effort) & resistance (load) forces are on thesameside of the fulcrum ii. heresistance forcealways has a mechanical advantage T iii.Examples 1. Biceps acting at the elbow 2. Quads acting on the knee (tibia) 3. Most open-chain kinetics 5. M uscle fibers, types, and descriptions a. b. Muscle fibers types i. The metabolic pathways in which they generate ATP & the rate at which its energy is made available to the contractile system of sarcomeres ii. Type I 1. Slow twitch oxidative (SO) 2. Low myosin ATPase & slow contraction time 3. High mitochondrial content 4. Difficult to fatigue due to high rate of blood flow 5. Suited for prolonged low-intensity work 6. Color: red (b/c of the high myoglobin content) 7. Holding a posture over time; long duration endurance type of activities iii. Type II-A 1. Fast twitch oxidative glycolytic (FOG) 2. Considered asintermediateb/c their fast contraction time is combined with a moderately well-developed capacity for both aerobic (oxidative) & anaerobic (glycolytic) activity 3. This type can maintain high contractile activity for longer periods 4. Used for stop-start sports such as football/tennis/basketball iv. Type II-B 1. Fast twitch glycolytic (FG) 2. Color: white (b/c of the little myoglobin & few capillaries) 3. Fatigue quickly 4. Large diameters a. Allows to produce great tension but only for short periods of time before they fatigue 5. Used for heavy weightlifting/powerlifting v. vi. s the demand peaks, greater/more sustained muscle power is achieved by recruitment of larger motor A units composed of Type IIA (FOG) Fibers and eventually Type IIB (FG) Fibers 6. Bones and where fractures begin a. Cortical bone vs. Cancellous bone i. Cortical boneis stiffer & can withstand greater stress but less strain before failing 1. Counteracts strength but does not have the flexibility to allow for strain 2. Denser than cancellous bone 3. Yields & fractures when strain exceeds1.5-2% ii. Cancellous bonehas a larger capacity for kinetic energy storage & can withstand more strain before yielding 1. Can withstand50%strain before a fracture occurs b. Bone stress injury i. The inability of a bone to withstand repetitive mechanical loading → results in structural fatigue & localized bone pain ii. Begins with a stress reaction & progresses to a stress fracture iii. Half of BSI’s are in long-distance runners 1. Typically at the tibial diaphysis iv. The exact location & characteristics depend on an individual's specific skeletal loading pattern . Newtons 1st, 2nd and 3rd Law and examples 7 a. First law i. States that if the vector sum of the forces acting on an object is zero, the object will remain at rest or remain moving at a constant velocity ii. “An object at rest stays at rest” iii. "Objects Keep Doing What They’re Doing" b. Second law i. Force = mass x acceleration (F = ma) ii. A net force on an object will change its velocity iii. "More Force = More Acceleration" iv. Acceleration is proportional to sum total of the magnitude + direction of the forces 1. It is opposed by friction c. Third law i. For every action, there is an equal and opposite reaction ii. The force that object 1 exerts on object 2 is of the same magnitude & in the opposite direction as the force that object 2 exerts on object 2 iii. "Every Action Has an Equal and Opposite Reaction" iv. When one object pushes on another, the second object pushes back with equal force . d 8. Degrees of freedom a. Refer to #2 9. Innervation ratio a. # of muscle fibers per motor neuron b. Small innervation ratio → more fine control of movement i. ex) eye muscles c. Large innervation ratio → less refined activation pattern d. Muscle fibers within a given motor unit contract or relax simultaneously i. Certain parts of a motor unit can't contract while other parts are relaxed 1. All-or-none law 10.Stress-Strain Curve (Young's modulus value) a. Used for a structure composed ofsomewhat pliablematerial b. Three major points i. If a load is applied within theelastic rangeof thestructure, no permanent deformation occurs ii. If loading continues past theyield point& into thestructure’splastic range, permanent deformation occurs iii. If loading continues within the plastic range,theultimate strain/failure point is reached c. Thetoe regionof the Stress-Strain Curve i. Represents the “settling” of the structure/material being tested or loaded d. Theelastic regionof the Stress-Strain Curve i. The region where the structure/material can revert back to its natural form if the deforming stress has been removed ii. The region is a prime example ofHooke’s law, which states that stress in a material is directly proportional to strain so long as the elastic limit has not been exceeded iii. The elastic limit is the end of the elastic region of this curve 1. If this limit is exceeded, the structure is said to have yielded, making it the yield point e. Theplastic regionof the Stress-Strain Curve i. The region that represents when the elastic limit of a material is exceeded ii. Resulting in lengthening & deformation of a tissue proportional to the applied load iii. What happens to biological tissues if there’s permanent plastic alteration? 1. b/c they havebiological memory, they arean exception to permanent plastic alteration 2. They will regain their original dimensions, even following plastic deformation f. Theultimate stress regionof the Stress-Strain Curve i. Occurs at the peak of the Stress-Strain Curve ii. Represents themaximum loadthat a tissue or structure can tolerate 1. Anything beyond this results in failure of the tissue g. Thenecking regionof the Stress-Strain Curve i. The period following anything past the ultimate stress = the failure of the tissue ii. Tissues under tension willrapidly narrowin the regionof failures 1. This narrowing is the “necking” of the structure h. Failure point/ultimate strain of the curve i. When there is a sudden decrease in stress while the strain continues to rise 1. This leads to acomplete rupture i. Young’s modulus i. The ratio of stress & strain in the elastic region of a particular material ii. States that thestiffnessof a material is represented by the slope of the curve in the elastic region 1. Which is obtained by stress/strain iii. 11.Muscles and angle of pennation a. Angle b/wlongitudinal axis(central tendon) of the whole muscle &its fibersin a pennate muscle b. This is what determines the range & power production of a muscle c. Pennation: The range of contraction is reduced to gain more power i. The most range-efficient arrangement for the muscle’s line of action is to be parallel to the muscle fibers d. If the angle is small → more range & less power e. If the angle is large → less range & more power i. Shorter & stronger contraction f. 12.Agonist muscle or group a. Prime mover b. Contracting muscle that is considered to be the principal muscle producing joint motion c. A muscle that makes amajor contribution to movement at the joint d. Always contracts actively 13.Antagonist muscle or group a. Muscle that opposes the prime mover b. Neither assists nor resists the motion of the primary mover (agonist) but rather itpassivelyelongates topermit the motion to occur c. Releases as the agonist moves through its ROM 14.Open and closed kinetic chains a. Kinetic chain i. Series of rigid segments connected by movable joints ii. The entire human body should be kinetic chain b. Closed kinetic chain (CKC) i. Both ends of the chain are constrained in the way they are permitted to move 1. Constraints: a. Mechanical, such as the friction b/w the foot & ground b. Functional, such as the balance requirements that compel the proximal end of the LE during weight-bearing ii. Most stuff is in the upright position 1. Maintenance of upright balance & control 2. Need to maintain gaze on visual targets 3. Need to keep the head horizontal for visual/vestibular orientation c. Open kinetic chain (OKC) i. Movement system in which at least one end of the chain isfree to move ii. Generally functional only when the proximal extremity end is stabilized & the distal end is free to move iii. The upper extremity acts as an open chain when reaching, placing, or throwing overhead iv. Characteristics 1. Any link in the chain is free to move independently of the others 2. Relatively large displacements are attainable 3. Relatively higher velocities are possible 4. Less force/power can be generated as compared to CKC activities v. vi. Lower extremities perform kicking & is in the wing phase of gait during OKC d. Throwing: OCK e. Pushing: CCK f. Spine operation i. CCK: upright position ii. OCK: horizontal position & when there needs to be some net displacement of the cephalad portion of the spine (i.e. forward bending) 15.Static equilibrium a. When a body or system is at rest or in constant motion b. For a biomechanical system to be in equilibrium i. The sumo of the forces acting on the systemmustequal zero (aka NO acceleration) 16.Quadriceps (Q) angle a. The angle formed between thehip, patella, and tibia b. Measures thepull of the quadriceps on the patella(laterally) and how it aligns within the knee joint c. The Q angle (quadriceps angle) is the angle formed between: i. A line from the hip (ASIS - anterior superior iliac spine) to the patella ii. A line from the patella to the tibial tuberosity d. A larger Q angle → a greaterlateral pull on the kneecap i. Which may increase the risk of knee problems e. Normal Q angle allows proper tracking of the patella (kneecap) during movement. f. Excessively large Q angle can cause kneecap instability, knee pain, and injuries like: i. Patellofemoral Pain Syndrome (PFPS) (runner’s knee) ii. Knee valgus (knock knees) iii. ACL injuries g. When our hip collapses in a valgus manner, the Q angle is increased → displaces patella laterally i. This causes erosion of the articular surface on the lateral aspect of the trochlear groove of the femur → tightness of the iliotibial band aka runner’s knee h. Normal range i. Men: 10-15° ii. Women: 15-20° 17.Anisotropy a. Quality of materials (i.e. bone) exhibiting different mechanical/physical properties when loaded or stressed along different axes or planes i. he way materials (like bone) have different mechanical or physical properties depending on the T direction of the force applied. 18.Lever systems (Type 1,2 and 3) a. Refer to #4 19.Fixed pulleys a. Refer to #1 20.Torsional loading/stress a. Types of applied forces (5) i. Tension, Compression, Bending, Shear, Torsion (twisting) 1. Torsion involves tension, compression, shear stresses ii. Compression loading 1. Occurs as a result of gravity and/or muscle contraction a. Boneis the tissue most exposed to compression loads & is by far the best designed to tolerate, absorb & counteract compression loading iii. Tensile loading 1. Occurs as a result of tissue being pulled apart 2. Most often occur within the musculotendinous unit a. Also occur in tendons, fascia, ligaments & bones 3. Can be beneficial such as in providing structural support to elements of the body (i.e. iliotibial banc) a. But excessive tensile loading is injurious, as we see with plantar fasciitis or Achilles tendinopathy iv. Torsional loading 1. Occurs as a result of applied torques & are a combination of tension, compression & shear stresses on body tissues a. Involve a twist such as in wringing out a damp cloth 2. Bone & non-contractile connective tissues absorb most of the imposed torsional loads 3. Can affect CT (like DM pts) resulting in shortening contractures or adversely affecting tendons a. I.e. twisting shortening of an unhealthy Achilles → multiple foot & ankle pathologies 4. May also contribute to the displacement of the nucleus pulposus of the intervertebral disc v. Shear loading 1. Occurs at right angles to the long axis of a structure 2. The tissues of the body are the most vulnerable to shear than any other type of load a. Shear-related injury occurs when a ski hits a tree stump. There is a shear load mostly at the level of the top of the ski boot vi. Bending loading 1. Common in the body & are the most significantly absorbed by bone 2. At least three application points are required & one of them must oppose the other two 3. It is a combination ofcompression, tension & shearstresses 21.Biological memory a. Refer to #10, plastic region b. Biological tissues are an exception to permanent plastic alteration b/c of the biological memory 22.Loads (shear, Tensile, compression, torsional) a. Refer to #20 23.Arthrokinematic/intra-articular movement of spin a. Accessory movements of joint surfaces within the actual joint space i. Rolls, spins & slides (aka translation or glides) 1. Roll: angular or curvilinear motion in which one bony articular surface rolls on the other 2. Spin: intrinsic joint movements about a longitudinal axis perpendicular to the articular surface . Slide: linear motion of one joint surface over the other 3 ii. “These accessory motions are crucial for proper joint motion” b. Subtle arthrokinematic shear i. The tangential component of an acting muscle force may cause arthrokinematicshearat the joint either with or w/o gross segmental movement 1. Even though the bone doesn’t move, there can still be movement within a joint 24.Synchondroses a. Cartilaginous joints i. Joints in which the bones are attached by cartilage ii. Allow for very little movement iii. Types 1. Synchondroses a. Bones joined together by hyaline cartilage b. ex) sternocostal articulations, physis, or epiphyseal region of long bones 2. Symphyses a. Hyaline cartilage covers the end of the bone but the connection b/w bones occurs through fibrocartilage b. ex) joints b/w vertebral bodies & pubic symphysis 25.Bone strain injuries a. Damage caused by excessive strain (deformation) of the bone due to external forces. b. Cause: High force applied to the bone → microdamage. c. Strain refers to the bone’s deformation, which can contribute to astress injury over time. d. Mechanical concept(how much a bone deforms under force) Bone Stress Injury (BSI) e. Progressive overuse injury caused by repetitive loading that exceeds the bone’s ability to repair itself. f. Cause: Repetitive stress from activities like running or jumping. g. Stages: i. Mild: Bone stress reaction (no fracture yet) ii. Severe: Stress fracture (tiny crack in the bone) h. Clinical result(actual damage due to repeated strain) i. Ex) Shin splints progressing to a tibial stress fracture. ** Think of rubber band: Strain = how much it stretches Stress = If stretches too often, it weakens and eventually breaks (stress injury) 26.Young's modulus of elasticity a. Refer to #10 b. Young modulus of elasticity is a measure of a material’sstiffness 27.Ground reaction forces a. The force exerted by the ground on a body in contact with it b. Always equal in magnitude & opposite in direction to the force that the body exerts on the ground c. Which way does it project? i. Upward from the foot → produces movement at each LE joint along the kinetic chain d. Peak vertical GRF: i. 120% of body weight when walking ii. 275% of body weight when running e. Examples i. A 150 lb male w/ a step length of 2.5 ft walking at 2110 steps per mile is loading his foot by 94.95 tons per foot, per mile ii. The same male running foot is exposed to around 275% of body weight at heel strike and subsequently 217.6 tons per foot, per mile 28.Center of gravity (COG) a. Two theories i. Focus of all gravitational forces (directed towards the center of our planet) 1. The point through which the sum of gravitational forces on a body can be considered to act ii. Central point of total mass 1. The point at which the total mass of a body or system is assumed to be centered b. Any change in any individual segment causes a change in the position of the center of gravity of the extremity & body as a whole . Location of COG of head, arms & trunk (HAT): anterior toT11& just below c the xiphoid process of the sternum i. The weight of HAT is approx. equal to 60% of the body weight d. Location of COG of the human body: anterior toS2 29.Creep a. Two basic phenomena that define theviscoelasticity of a structure i. Creep 1. Progressive deformation of a structure under a constant load 2. Typically see a rapid initial deformation followed by a slow progressively increasing deformation 3. When does it occur? a. When a viscoelastic load is subjected to the action of a constant load 4. Example a. Progressive stretching of annulus fibrosis as a result of sitting for prolonged periods of time with the lumbar spine in forward bending ii. Stress relaxation 1. Decrease of stress within a structure in the presence of a constant strain b. Strain-time curve i. Shows the progression of deformation over time & therefore, best illustrates the phenomenon of creep ii. Creep ceases when the compressive stress developed within the solid matrix issufficient to balancethe applied load iii. At this point, no fluid flows outward across the semipermeable membrane & the equilibrium point has been reached 1. Fluid does NOT flow at creep equilibrium 30.Transverse foramina a. Round window in the transverse process that houses and protects the vertebral artery, vein, and sympathetic nerve plexus b. Where the vertebral artery and vein pass through i. Transverse foramina of cervical vertebrae, typically C1-C6 ii. 31.Vertebral bodies a. Of Cervical spine i. Small and wider from side to side than anteroposteriorly 1. Superior surface concave with uncus of body (uncinate process) 2. Inferior surface convex ii. C1 lacks vertebral body b. Of Thoracic spine i. Heart-shaped; one or two costal facets for articulation with the head of a rib ii. Typical thoracic vertebrae bear superior & inferior half facets, called demifacets 1. The demifacets are on the superior & inferior edges of the lateral aspects of the vertebral bodies 2. The vertebral body of any typical thoracic vertebra (T2-T9) articulates w/ four rib heads a. One superolaterally & one inferolaterally on each side c. Of Lumbar spine i. assive; kidney-shaped when viewed superiorly M ii. Larger & have NO costal facets iii. Composed of 1. Inner: cancellous bone (spongy or trabecular bone) 2. Outer: cortical bone (compact bone) iv. The lumbar vertebra is the thickest at the region of the end plate v. Provides a rim for the attachment of the disc, muscle, and ligaments 32.Anterior Longitudinal ligament a. Blends with annulus fibrosis b. 2x stronger than PLL c. Prevents hyperextension i. This is why we have more support when bending backward than forward . d e. Tension in the ALL is in extension 33.Ligamenta Flava . a b. Very elastic ligament & therefore, stores kinetic energy to assist with spinal extension 34.The different facet joints, their orientation, and the predominant movement they allow a. i. Facet joints guide intervertebral motion ii. Covered by hyaline cartilage iii. Enveloped by a loose fibrous capsule Facets in the spine b. Cervical spine i. Superior facets: directed superoposteriorly ii. Inferior facets: directed inferoanterioly iii. Oblique-placed facets: most nearly horizontal iv. c. Thoracic spine i. ii. Typical thoracic vertebrae bear superior & inferior half facets, called demifacets 1. The demifacets are on the superior & inferior edges of the lateral aspects of the vertebral bodies 2. The vertebral body of any typical thoracic vertebra (T2-T9) articulates w/ four rib heads a. One superolaterally & one inferolaterally on each side iii. T1: A superior facet is not a demifacet iv. T10: a single pair of whole facets v. T11 & T12: each has a single pair of entire costal facets (located on the pedicles) . L d umbar spine i. 35.Kirkaldy-Willis Model of Degenerative Disc Disease a. Spinal degeneration as the result of a complex interaction b/w the intervertebral discs and the 2 facet joints i. There is a segmental dysfunction resulting from a cumulative or single trauma ii. There is a long phase of relative instability at that spinal segment along with intermittent bouts of back pain iii. The bodyrestabilizes the segment& the patient experiences fewer episodes of back pain b. Phase I (dysfunction) i. Normal function of the joint complex is interrupted ii. Physical examination will reveal hypertonicity iii. Gross movement is reduced c. Phase II (unstable) i. Patient has abnormal, increased movement ii. Laxity of posterior joint capsule & annulus fibrosis is seen in autopsy d. Phase II (stabilization) i. Unstable segmentregains stabilitysecondary to fibrosis & osteophyte formation 36.Stress relaxation a. One of the two phenomena that define the viscoelasticity of a structure i. Decrease of stresswithina structure in the presence of aconstant strain b. Occurs when a viscoelastic solid is subjected to aconstantdeforming force c. Example i. Dynamic splints 1. They are used to increase joint ROM 2. Initially, they are uncomfortable & unyielding but as time passes, the device begins to feel more comfortable . d : stress reduction over time e. Creep & stress relaxaion i. They occursimultaneously ii. Mechanism 1. Internal friction a. Caused by long polymeric chains sliding on one another b. Responsible for viscoelastic behavior oftendons & ligaments 2. Outflow of interstitial fluid a. Causes compressive viscoelastic behavior ofcartilage 37.Creep a. Refer to #29 38.Joint reaction forces a. Equal and opposite forces that exist at a joint b/w adjacent bones i. The result of the weight and inertial forces of the two segments b. Occurs in jointssecondary to the primary forces of muscle contraction or gravity c. Example i. When a primary force produces distraction of a joint (like holding a suitcase or weight), the JRF will be a compression directed force produces by muscles & ligaments d. The amount of JRF is typically high i. b/c most muscles attach at an acute angle to the bone e. The muscle must generate a relatively large force to produce an effective rotary (tangential) component i. Generates a large stabilization or joint compression component (radial component) f. In the hip, it is the result of the need to balance the moment arms of the body weight and abductor tension g. JRF i. 2W during SLR ii. 3W in single-leg stance iii. 5W in walking iv. 10W while running 39.Innervation ratio a. Refer to #9 40.Properties of tendons and ligaments a. Tendons & ligaments areparallel-fibered collagenous tissues i. Composed oftype I collagen ii. This type of collagen is best suited to resist tensile loads iii. Collagen is a fibrous protein constituting approx. ⅓ of the total protein in the body b. Ligaments i. Strong, moderately pliable, and flexible 1. Allows for adequately guided and controlled movements of the articulating bony segments . Minimally extensible 2 3. These properties allow for suitable stabilization, control, and guidance of joint motion c. F ibers alignment i. d. Composition & structure i. Tendons & ligaments consist of relatively few cells (fibroblasts mature into fibrocytes) & an abundant ECM 1. Fibroblasts are actively involved in producing the components of the tissue 2. Fibrocytes maintain and repair tissue when needed ii. 20% cellular material + 80% ECM 1. ECM = 70% water + 30% solids (collagen, ground substance, elastin) e. Tendon structure & composition i. Biomechanically designed to resist the longitudinal stress (generated by muscle and the GRF) ii. Chains of tropocollagen are longitudinally arranged → united into fibers iii. Endotendon 1. Organize and hold fibers in a linear direction → forms fascicles iv. Epitenon 1. Packs fascicles continuous with the endotenon 2. Provides for its microvasculature f. Mechanical behavior i. Both tendons & ligaments are designed to resist primarily tensile loads during normal and moderately challenging loadings ii. Excessive or abnormal loading → injury 1. The degree of the trauma or damage is related to the quality of the tendon, the rate of impact, the amount of load, and the integrity of the other related supporting structures 41.Joints and planes of motion a. b. c. . d 42.Cauda Equina Syndrome a. Cauda equina i. Collection of nerve roots at the inferior end of the vertebral canal b. Cauda equina syndrome i. Areflexic bladder, bowel controls 1. May also include urinary retention & saddle paresthesia of lower limbs ii. Most commonly caused by massive midline disc herniationbelow L1 43.Neurapraxia a. Three types of nerve injuries i. Axonotmesis ii. Neurotmesis 1. Most severe iii. Neurapraxia 1. reversible interference with nerve conduction due to compression 2. transient cessation in nerve function 3. May lead to temporary loss of motor or sensory function 4. Spontaneous recovery occurs in a few hours, days, or weeks a. Average 6-8 weeks *-tmesis: cut **
