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Joint Structure Function Comprehensive Analysis 5th Edition Levangie Norkin -Test Bank
Chapter 2: Joint Structure and Function
Identify the choice that best completes the statement or answers the question.
____ 1. Which of the following statements is true concerning fibroblasts?
|a.||They synthesize the extracellular matrix of connective tissue.|
|b.||They are not normally present in healthy connective tissue.|
|c.||They are undifferentiated precursor cells.|
|d.||They are circulating cells.|
____ 2. Which of the following statements is true concerning nutrition of articular cartilage?
|a.||Articular cartilage can easily repair itself due to its very efficient and effective nutritional system.|
|b.||Nutrients are found in large proportions in the more superficial layers of articular cartilage.|
|c.||Nutrients from synovial fluid can pass into articular cartilage when external pressure is applied.|
|d.||All forms of joint loading will cause poor nutrition to articular cartilage.|
____ 3. Which of the following statements is true concerning articular cartilage injury?
|a.||A superficial laceration is capable of healing itself by filling in with fibrovascular tissue.|
|b.||A deep cartilage lesion does not extend beyond the tidemark.|
|c.||A deep laceration may heal by forming new fibrocartilage.|
|d.||A superficial lesion is likely to heal faster than a deep one.|
____ 4. Which of the following best describes the structural composition of the extracellular matrix of bone?
|a.||Glycosaminoglycans, glycoproteins, water, and proteoglycans|
|b.||Collagen fibers, glycosaminoglycans, water, and mineralized bone salts|
|c.||Collagen fibers, glycosaminoglycans, glycoproteins, water, proteoglycans, and mineralized bone salts|
|d.||Glycosaminoglycans, glycoproteins, water, proteoglycans, and unmineralized bone salts|
____ 5. Which of the following statements is true concerning the biomechanical properties of ligaments, if the rate of application of the force is increased?
|a.||The ligament stores less energy to failure.|
|b.||The ligament requires more force to rupture.|
|c.||The ligament has decreased stiffness.|
|d.||The stiffness of the ligament is unchanged.|
____ 6. For the stress-strain curve in Figure 2-6, identify the point of ultimate failure.
____ 7. The plastic portion of the stress-strain curve pictured above lies between:
|a.||Point A and point B|
|b.||Point A and point D|
|c.||Point B and point D|
____ 8. In Figure 2-7, point A can best be describes as:
|a.||The point indicating the end of the elastic modulus|
|b.||The point where permanent deformation of the tissue begins to occur|
|c.||The point where uncrimping of the tissue ends|
|d.||The point where the greatest amount of force is being applied|
____ 9. As a clinician, you are attempting to produce permanent elongation in a severely contracted flexor digitorum profundus tendon. Which of the following general strategies concerning treatment will be least effective in achieving permanent lengthening of the tendon?
|a.||Apply force slowly to decrease the stiffness of the tendon.|
|b.||Apply a short duration force, keeping the force in the elastic range.|
|c.||Apply enough force to cause microfailure of some fibers in the tendon.|
|d.||Use a splint that will apply a low load to the tendon (at the beginning of the elastic range) for 3 weeks.|
____ 10. When describing the biomechanical properties of cancellous and cortical bone, which of the following statements is true?
|a.||Cancellous bone is stiffer than cortical bone and can withstand less strain before failure.|
|b.||Cortical bone is stiffer than cancellous bone and can withstand less strain before failure.|
|c.||Cancellous bone is stiffer than cortical bone and can withstand more strain before failure.|
|d.||Cortical bone is stiffer than cancellous bone and can withstand more strain before failure.|
____ 11. When a bone is repeatedly loaded with low-level forces over an extended period of time, fatigue fractures may occur within the bone. This is due to:
|a.||Increased stiffness, decreased yield strength, increased permanent deformation|
|b.||Decreased stiffness, increased yield strength, no effect on deformation|
|c.||Decreased stiffness, decreased yield strength, increased permanent deformation|
|d.||Increased stiffness, increased yield strength, no effect on deformation|
____ 12. Which of the following is true about the biomechanical properties of a ligament (or tendon) if the width of the ligament is doubled?
|a.||Greater elongation before failure|
|b.||Less elongation before failure|
|c.||Increased strength before failure|
|d.||Decreased strength before failure|
____ 13. Which of the following joints has two or more degrees of freedom of osteokinematic motion?
|a.||Third proximal interphalangeal (PIP) joint|
|b.||Superior radioulnar joint|
____ 14. Which of the following would constitute a closed kinematic chain activity of the left shoulder complex?
|a.||Using your left arm to push yourself out of a chair|
|b.||Throwing a Frisbee with your left hand|
|c.||Combing your hair with your left hand|
|d.||Waving with your left hand|
____ 15. Which of the following statements is true concerning joint play of a joint?
|a.||Joint play is not considered a normal motion at the joint.|
|b.||They must be tested by application of an external force.|
|c.||They can be performed voluntarily by a subject.|
|d.||They occur only in the close-packed position of the joint.|
____ 16. A man is sitting on a chair. He brings himself up into a standing position. His tibiofemoral joint moves from a flexed position to full extension during the maneuver. Which of the following best describes what is happening at the tibiofemoral joint during this maneuver? Think in anatomical terms.
|a.||Anterior glide of the proximal tibia on the distal femur|
|b.||Posterior glide of the proximal tibia on the distal femur|
|c.||Anterior glide of the distal femur on the proximal tibia|
|d.||Posterior glide of the distal femur on the proximal tibia|
____ 17. Which of the following statements is true concerning the close-packed position of any joint?
|a.||Capsular structures are loose.|
|b.||Ligaments around the joint are slack.|
|c.||The joint is relatively easy to separate with distraction.|
|d.||There is a maximum area of surface contact occurring.|
____ 18. Cartilage primarily receives its nutrition from ____________________.
|a.||its high level of permeability|
|c.||a process of joint loading and unloading|
____ 19. Which of the following statements is true regarding articular cartilage injury?
|a.||A deep cartilage lesion does not extend beyond the tidemark.|
|b.||A deep laceration may heal by forming new fibrocartilage.|
|c.||A superficial lesion is likely to heal faster than a deep one.|
|d.||A cartilage injury cannot heal.|
____ 20. Increasing the rate of application of a force causes a ligament to ____________________.
|a.||store less energy to failure|
|b.||require more force to rupture|
____ 21. To increase a patients wrist extension range of motion by using an accessory motion gliding technique, the therapist would want to perform a(n) ____________________.
|a.||posterior glide of the carpals on the radius|
|b.||anterior glide of the carpals on the radius|
|c.||anterior glide of the radius on the carpals|
Chapter 2: Joint Structure and Function
Connective tissue is made of cells and extracellular matrix. Fibroblasts are a type of resident cell that not only serves a role as the cellular component but actually synthesizes the extracellular matrix in which the cells reside. Fibroblasts play a large role in the synthesis of collagen, which is the fibrillar component of most extracellular matrixes.
Articular cartilage in adults is highly porous, but compression is necessary to allow for fluid mechanics, which will provide nutrition to the multiple layers of the structure. Articular cartilage is devoid of blood vessels in adults, and a movement of fluids caused by intermittent compression and rest to the cartilage allows nutrients to be carried from the deeper layers, closer to the subchondral bone (where there is a blood supply), to the more superficial layers.
Unless an injury breaks through the uncalcified cartilage layer, known as the tidemark, it is unlikely that it will heal. If an injury breaks through this layer, it is likely that the blood supply from the subchondral bone may play a role in forming new fibrocartilage in place of hyaline cartilage. This may lead to endochondral ossification over time, but it is the only opportunity cartilage has for self-repair.
Each extracellular matrix has a combination of fibers (collagen) and an interfibrillar component (proteoglycans and glycoproteins). The proteoglycans can further be broken down into polysaccharide chains called glycosaminoglycans (GAGs). In addition to this normal combination of components, bone contains mineralized bone salts (calcium and phosphate crystals), which give this structure its hard surface.
All viscoelastic tissues exhibit rate-dependent properties that cause a change in tissue behavior based on rate of application of a force. When viscoelastic materials are loaded rapidly, they exhibit greater resistance to deformation than when loaded more slowly and require more force to failure than when loaded more slowly.
The point of ultimate failure occurs at the end of the plastic region when the material has undergone maximal deformation and has ruptured.
This is the region of the stress-strain curve where permanent deformation takes place.
In tendon and ligaments, collagen fibers are reported to straighten out during the initial application of a force.
If a muscle has undergone prolonged shortening and is now considered to be in a state of contracture, one must make permanent changes in the stress-strain curve of that tendon in order to regain the length of the structure. There are several ways to accomplish changes in the stress-strain curve of a tendon. One of the most effective ways to apply a low load over a long period of time is to utilize the phenomenon of creep to cause permanent deformation. Another way to address this issue is to push the fibers to the end of the plastic range or slightly into the plastic region of the stress-strain curve, causing microfailure of the structure and thus causing permanent change in length.
The stress-strain curves for cortical and cancellous bone are different. The tougher, outer cortical bone is stiffer than cancellous bone. This means that it can withstand greater stress but less strain than cancellous bone.
Repeated loading of bone can cause permanent strain and lead to bone failure. Bone loses stiffness and strength as a result of creep strain.
The radiocarpal joint allows for motion in two different planes. Flexion and extension occur in the sagittal plane about a coronal axis, and radial/ulnar deviation occurs in the frontal plane about a sagittal axis. All of the other joints listed are uniaxial joints with only one degree of freedom.
Pushing yourself out of a chair using your arm would be considered a closed kinematic chain activity. Because the arm is bearing weight through the arms of the chair, which are in contact with the ground, this would mean that the distal segment is fixed, and the body is moving about this fixed segment.
Joint play is the movement of one articular surface on another that is not under voluntary control. The joint must be in a loose pack position in order to allow movement when an external force is applied.
The activity of rising from a chair would be a closed kinematic chain activity, which means that the proximal joint surface will be moving on the distal joint surface. In the case of the tibiofemoral joint, this means that the convex femoral condyles will move on the concave tibial plateau. Because this would constitute a convex surface moving on a concave surface, the roll and glide of the joint surfaces will occur in opposite directions. As the person comes to a standing position, the femur will roll in an anterior direction, and the joint surface will glide (or slide) in a posterior direction.
The closed-pack position of a joint occurs when there is maximal congruency between joint surfaces, and the ligaments and capsule are maximally tight. This position normally occurs at the end of range of motion and makes passive movement of the joint surfaces very difficult.
Although the synovial fluid providing nutrition to cartilage has a low degree of permeability allowing for some diffusion, the process of joint loading and unloading provides a larger-scale exchange of synovial fluid, allowing the more nutrition-rich fluid into the cartilage.
The interface between calcified and uncalcified cartilage is important to growth and healing.
Increasing the rate of loading causes increased stiffness in tissue, allowing less elongation but more force before failure.
This concept might be a bit more advanced, but students should understand that an arthrokinematic gliding motion anteriorly at this joint will support the osteokinematic motion of wrist extension.
The outer layer (zone I) has parallel fibers suited to the function of reducing friction between contacting surfaces. The middle layer (zone II) is a lattice-work arrangement, allowing this layer to change shape to absorb shock and squeeze fluid in and out. The inner layer (zone III) contains fibers that are also aligned perpendicular to the bone surface to secure the tissue into the calcified layer of cartilage (zone IV).
When cartilage is compressed, the protein molecules (proteoglycans and glycoproteins) release some of the water content that is squeezed into or out of surrounding tissues. Collagen fibers may permit deformation of the tissue. The proportion of fluid exuded and tissue deformation are dependent upon the magnitude, rate, and duration of load. When a load is sustained for a period of time, the permeability of the cartilage decreases over that time period. Similarly, the rate of deformation is indirectly proportional to the magnitude of applied load. That is, for a unit compression of 1, the cartilage deforms unit 1. For a unit compression of 2, the cartilage may only deform an additional 1/2 unit.
Viscoelastic materials exhibit elasticity (ability to deform and return to its original shape immediately) and viscosity (ability to resist shear). Viscosity gives the tissues time and rate-dependent properties; that is, the deformation response of the tissue varies according to the duration of load and the rate of load. Each of the tissues listed above is viscoelastic.
Stress is the force applied to a tissue per unit area. Strain is the deformation that occurs in a tissue in response to an applied stress and is expressed as the change in shape (length, width) over its original shape (length or width). Stresses and strains may be tensile, compressive, shear, or torsional.
The modulus of elasticity is the ratio of stress to strain at any point in the stress-strain curve. A large applied load that results in only a small deformation will have a high modulus of elasticity. The steeper the stress-strain curve, the higher is the modulus of elasticity. Because the material does not readily respond to an applied load, it is considered stiff (therefore, stiffness is equivalent to the modulus of elasticity). A tissue is brittle when the plastic region is very small or absentthat is, the material undergoes very little deformation prior to ultimate failure. A ductile material, in contrast, can undergo considerable deformation prior to failure.
Synovial fluid, which is produced by the synovial layer of the capsule, is composed primarily of plasma and hyaluronic acid, with a glycoprotein called lubricin. Hyaluronate is responsible for reducing friction between the synovium and joint surfaces, and lubricin reduces friction between the joint surfaces (cartilage-on-cartilage).
Spin is rotation about a fixed axis. Slide is a pure translatory or linear movement of one surface upon another, and roll would be rolling of one surface upon another (as in a rocking chair). Generally, intra-articular surfaces slide and roll upon one another in an attempt to produce as close to a pure spin as possible. This is rarely, if ever, achieved.
The responses can be numerous. Because the collagen fibers in tendons, ligaments, and capsules orient themselves according to the tensile stresses imposed, reduction in these stresses will result in a random arrangement of fibers which, once stresses are reimposed, cannot resist heretofore normal magnitudes of load. There is also a loss of proteoglycans (therefore water). Both the water loss and the random arrangement of fibers result in a tissue that is stiffer and will move more rapidly to failure, especially at points of insertion. Cartilage, which is dependent upon compression and release for nutrition, will gradually deteriorate. Because the trabeculae in cancellous bone respond to imposed stresses, reduction of stresses will result in thinning of trabeculae and reduced strength of the bone (more readily fracturing under smaller loads).
Sustained loads on tendons, ligaments, or cartilage can lead to excessive deformation (plasticity) and threat of failure. Repetitive loading may reimpose a load before a tissue has returned to its initial state, thus increasing the likelihood of exceeding the yield point (elastic limit), resulting in inflammation and microfailure.
Mobility of joints is assessed passively and refers to the amount of motion that is available (rather than that which someone necessarily uses actively). Hypermobility refers to excessive joint mobility. It generally results from inadequate support from structures such as joint capsule or ligaments (torn ligaments, plastic ligaments, or high elastin content). Hypermobility may also result from inadequate muscular support (e.g., weak or hypotonic muscles) around the joint. Hypomobility refers to limited joint mobility. It generally results from bony limitations to motion (e.g., large bony prominences, bone spurs), adaptively shortened joint capsule or ligaments, or excessive muscle support around the joint (e.g., hypertonic muscles or adaptively shortened muscles).
Chapter 12: The Ankle and Foot Complex
Identify the choice that best completes the statement or answers the question.
____ 1. Which of the following is a primary function of the foot?
|a.||The foot serves as a rigid lever to increase efficiency during push-off.|
|b.||In supination, the foot becomes a mobile adapter in order to adapt to changes in the terrain.|
|c.||The foot assists with shock absorption but is not the bodys primary shock absorber.|
|d.||The foot absorbs rotation of the lower limb by pronating and supinating.|
____ 2. Your patient was casted and presents with limited plantarflexion range of motion (ROM) at the talocrural joint. What associated movements at the superior tibiofibular joint would you expect to be limited?
|a.||Cephalic fibular glide and medial rotation|
|b.||Cephalic and posterior fibular glide|
|c.||Caudal fibular glide and lateral rotation|
|d.||Caudal and anterior fibular glide|
____ 3. Your patient injured his ankle when landing with his foot and ankle in an inverted and plantarflexed position. A ligament that limits these motions is torn. Which of the following ligaments would most likely be torn with this type of injury?
|a.||Posterior talofibular ligament|
|b.||Anterior talofibular ligament|
|c.||Superior fibers of the deltoid ligament|
|d.||Plantar calcaneonavicular ligament|
____ 4. The talocrural joint functions in the motion of dorsiflexion and plantarflexion. Due to triplanar motion at this joint, what other motion occurs with dorsiflexion?
____ 5. During supination at the subtalar joint, the axes of the transverse tarsal (midtarsal) joints become ____________________, resulting in greater ____________________ of the foot during gait.
____ 6. Your patient demonstrates decreased open chain pronation at the subtalar joint. Which of the following would be limited?
|a.||Eversion of the calcaneus on the talus|
|b.||Adduction of the calcaneus on the talus|
|c.||Plantarflexion of the calcaneus on the talus|
|d.||Both A and C are correct.|
____ 7. During closed chain pronation, ____________________.
|a.||the lower limb medially rotates, creating a flexion moment at the knee|
|b.||the lower limb laterally rotates, creating a flexion moment at the knee|
|c.||the lower limb medially rotates, creating an extension moment at the knee|
|d.||the lower limb laterally rotates, creating an extension moment at the knee|
____ 8. When a person supinates during a closed chain activity, the head of the talus dorsiflexes and ____________________ on the calcaneus while the calcaneus ____________________.
____ 9. You observe that your patient has excessive flattening of the medial longitudinal arch. You hypothesize that the excessive flattening is due to excessive lengthening of the ligaments that support the medial longitudinal arch. Which of the following structures would be excessively lengthened?
|b.||Posterior talofibular ligament|
____ 10. In standing, when the subtalar joint is in supination, what is happening at the midtarsal joints and the forefoot?
|a.||The midtarsal joint axes converge, and the forefoot supinates at the tarsometatarsal joints.|
|b.||The midtarsal joint axes become parallel, and the forefoot supinates at the tarsometatarsal joints.|
|c.||The midtarsal joint axes converge, and the forefoot pronates at the tarsometatarsal joints.|
|d.||The midtarsal joint axes become parallel, and the forefoot pronates at the tarsometatarsal joints.|
____ 11. Which of the following statements best describes the windlass mechanism of the plantar aponeuroses (fascia)?
|a.||Passive flexion of the big toe causes the medial longitudinal arch to elevate.|
|b.||Tension on the lateral calcaneus causes the lateral longitudinal arch to elevate.|
|c.||Passive extension of the big toe causes the medial longitudinal arch to elevate.|
|d.||Tension causes the axes of the midtarsal joints to become more parallel at push-off.|
____ 12. When performing resisted testing of your patients foot and ankle, you find that pain is reproduced only when resisting a muscle that supports the lateral longitudinal arch. Which of the following muscles would be painful with resisted testing?
|a.||Flexor hallucis longus|
____ 13. Which functions of the foot are best achieved by supination at the foot?
|a.||Provide an accommodative structure at heel strike.|
|b.||Assist in attenuating impact during early stance.|
|c.||Provide a rigid lever for push-off.|
|d.||Absorb transverse plane rotation of the lower limb.|
____ 14. Due to triplanar motion, which motion occurs at the talus with talocrual dorsiflexion?
____ 15. Which of the following combinations of ligaments makes up the primary ligamentous support of the medial longitudinal arch?
|a.||Short plantar ligament, cervical ligament, and long plantar ligament|
|b.||Short plantar ligament, spring ligament, and long plantar ligament|
|c.||Spring ligament, bifurcate ligament, and long plantar ligament|
|d.||Short plantar ligament, bifurcate ligament, and cervical ligament|
____ 16. The transverse tarsal joint is formed by:
|a.||Talocalcaneal joint and talonavicular joint|
|b.||Talonavicular joint and calcaneocuboid joint|
|c.||Calcaneocuboid joint and tarsometatarsal joint|
Chapter 12: The Ankle and Foot Complex
The foot serves as a rigid lever to increase efficiency during gait, especially during push-off. The foot also assists with shock absorption through pronation during heel strike.
The proximal tibiofibular joint moves with talocrural motion. During plantarflexion, the fibula glides caudal and anteriorly, and in dorsiflexion, the fibula glides cephalad and posteriorly.
During an inversion sprain, the ligaments of the lateral ankle would be overstressed. The most commonly injured ligament of this complex is the anterior talofibular ligament.
The ankle joint is considered to be triplanar because its axis for dorsiflexion-plantarflexion crosses all three planes. The ankle joint axis passes through the malleoli of the tibia and fibula. Rather than being a true coronal axis, the ankle joint axis is rotated laterally about 20 to 30. It is also inclined downwardly about 10 on the lateral side. The laterally rotated location of the axis gives the foot its apparent toe-out stance. An ankle joint axis rotated laterally in excess of 20 to 30 from the frontal plane indicates the existence of lateral tibial torsion. Less than 20 to 30 of inclination would be considered medial tibial torsion. Although not immediately obvious from examining the inclination, the orientation of the ankle joint axis results in dorsiflexion of the ankle being accompanied by movement of the tibia medially on the fixed foot (or movement of the foot laterally on the tibia when the distal lever is free). With this triplanar motion, there is also an abduction motion seen with dorsiflexion, and adduction accompanies plantarflexion.
There are two axes of motion. One axis allows for abduction and adduction; the other allows for inversion and eversion. These two axes can converge or diverge. During supination of the foot, the subtalar joint becomes more rigid, and the axes converge. During pronation, the axes become parallel and the foot becomes more mobile.
During open kinetic chain eversion of the subtalar joint, the calcaneus everts on the talus, and there is dorsiflexion of the talocrural joint. The opposite is true in closed kinetic chain activity.
During closed chain pronation, the talus drops medially, causing the tibia to follow in an inferior and medial direction and causing medial rotation. Due to this medial rotation of the tibia, the knee unlocks and flexes.
Due to the triplanar nature of the ankle, many motions occur in closed chain activity. During closed chain supination, the head of the talus dorsiflexes and abducts on the calcaneus, while the calcaneus inverts on the ground. In pronation, the talus plantar flexes and adducts, while the calcaneus everts.
The medial longitudinal arch is supported by a ligamentous complex. This complex includes the spring ligament and calcaneonavicular ligament.
The midtarsal joint converges with forefoot pronation during subtalar supination. During subtalar pronation, the midtarsal joint becomes divergent, and the forefoot supinates to maintain contact with the ground.
During push-off of the gait cycle, passive tension from the plantar aponeuroses causes the medial longitudinal arch to elevate.
The medial longitudinal arch is primarily supported by a ligamentous complex. Ligaments also help to support the lateral longitudinal arch but also receive dynamic support from the tibialis posterior and the peroneus longus tendon.
The convergence of axes in the supinated foot causes the foot to become rigid. This rigidity is necessary to create a solid lever for push-off of the foot.
While the motion of dorsiflexion primarily occurs in the sagittal plane, investigators have found transverse plane motion contributing to abduction of the talus with dorsiflexion and adduction with plantarflexion.
The medial longitudinal ligament is supported by the short and long plantar ligaments and the spring ligament.
This joint is also known as the midtarsal joint.
The talocrural joint includes the tibia and fibula proximally and the talus distally. The proximal articular surfaces are made up of the fibular malleolus, the distal tibia, and the tibial malleolus. The three facets together form what is known as the mortise, a three-sided surface equivalent to the working end of a wrench. The distal joint surfaces are the lateral facet of the body of the talus, the trochlea (superior surface) of the body of the talus, and the medial facet of the body of the talus. These three surfaces articulate with the lateral malleolus, distal tibia, and medial malleolus, respectively. The surface of the talocrural joint forms a congruent synovial hinge joint with one degree of freedom, although some small amounts of abduction-adduction and inversion-eversion of the talus within the mortise have been hypothesized.
The superior and inferior tibiofibular joints perform the function of maintaining the mortise while permitting some motion between the malleoli, which is necessary to permit full range of ankle motion. The superior tibiofibular joint is a plane synovial joint between the head of the fibula and the posterolateral tibial condyle. It has a separate joint capsule, which generally has no connection with the knee joint. The inferior tibiofibular joint is a syndesmosis, a fibrous union of the distal tibia and fibula. The two joints maintain the apposition of the tibia and fibula, assuring an appropriate (but slightly changing) grip of the mortise on the talus and, therefore, stability of the ankle joint.
The subtalar joint is composed of three different facets: a large posterior facet and two smaller medial and anterior facets. The posterior facet is convex on the calcaneus and concave on the talus. It is encompassed by its own capsule. The anterior and medial facets are concave on the calcaneus and convex on the talus. These two facets share a joint capsule with the talonavicular joint. The posterior joint capsule and the more anteriorly located facets are also separated by sulci on both the calcaneus and talus. When brought together, these sulci create the tarsal canal, which runs transversely through the hindfoot.
The close-packed position for the subtalar joint is supination. In this position, the ligamentum cervicis becomes taut, drawing the talus and calcaneus together. In weight-bearing, a lateral rotatory force on the leg will bring the talus laterally as well, carrying the subtalar joint into supination and locking it.
The transverse tarsal joint (TT) is a composite S-shaped joint that lies transversely across the foot. It is formed by the talonavicular joint medially and the calcaneocuboid joint laterally. The talonavicular joint is a fairly mobile plane joint that has already been described as part of the TCN. The calcaneocuboid is also a plane synovial joint, formed by two reciprocally convex-concave facets on the calcaneus and the cuboid. This facet shape requires that the moving segment move in opposite directions intra-articularly, limiting the motion that can take place.
The TMT joints only come into play when the TT joint proves inadequate. That is, when the TT joint cannot move sufficiently in one direction, the movement is augmented by the TMT joints.
When the subtalar joint is supinated, the transverse tarsal (TT) joint is also supinated. The locked hindfoot tends to press the lateral side of the foot into the ground. The fifth ray is pushed upward into dorsiflexion, and the first ray plantarflexes to get back to the ground. Fifth ray dorsiflexion and first ray plantarflexion result in the four outer rays rotating into eversion. This pronation twist of the TMTs is restricted in range but helps adapt the forefoot to the ground when the TT joint is not able to. Similarly, when the TT is fully supinated or pronated and more supination or pronation is required, the TMT will be called in to contribute.
Ligamentous support of the osseoligamentous plate is provided by the medially located plantar calcaneonavicular (spring) ligament, by the laterally located plantar calcaneocuboid (short plantar) and long plantar ligaments, and by the plantar aponeurosis.
As the body weight comes down the tibia, all the weight passes from the tibia to the body of the talus. From there, half of the weight moves posteriorly to the calcaneus and half moves anteriorly to the forefoot. Of the weight passing to the forefoot, two thirds pass through the talonavicular joint and one third through the calcaneocuboid joint. As the weight arrives at the heads of the metatarsals, the first metatarsal bears twice as much weight as the other four toes (which bear equivalent amounts to each other).
The metatarsal break is the metatarsal phalangeal (MTP) hyperextension that occurs around an oblique axis as the heel lifts in weight-bearing. The obliquity of the combined axis for flexion-extension of the MTPs results in more symmetrical weight-bearing across the toes as they extend than would occur if the axis were a true coronal axis. Although the first toe still receives much more weight than the other toes, the first would receive far more of the weight if it were not for the obliquity of the MTP axis. A decrease in the normal obliquity found among individuals with different toe configurations may result in excessive stress on the second and first toes.
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