Kinesiology-ankle-foot.docx

KINESIOLOGY: CHAP 11: ANKLE & FOOT Ankle et foot –consists of 26 bones, 34 joints et over 100 mm, tendons et ligaments

BONES 26 bones of the ankle et foot divided into: leg, tarsals, metatarsals et phalanges Leg bones include: tibia et fibula 7 tarsal bones, 5 metatarsal bones et 14 phalanges Leg bones:  Tibia -bears 90% of the body weight  Fibula – nonweight-bearing bone, carrying only 10% of the body weight Tibia – easily palpated from the tibial tuberosity; aka shin; medial aspect is not covered by mm Medial malleolus – the most distal aspect of the tibia; it is a prominent process of the enlarged distal portion of the tibia that forms a prominent landmark on the medial side of the ankle Tibial shaft – rotated laterally in the transverse plane as it traverses distally Plafond – the inferior aspect of the tibia is a saddleshaped structure -the ceiling or distal end of the tibia which forms the proximal surface of the talocrural joint Fibula – small bone that serves primarily as a site for mm et ligament attachments Lateral malleolus – the most distal end of the bone; -an easily observed landmark on the lateral aspect of the ankle Tarsal bones:  Rearfoot – comprises the talus et calcaneus -plays an important role in motions et positions of the midfoot  Midfoot – includes 5 tarsal bones: o Navicular o Cuboid o 3 cuneiforms  Forefoot 3 arches:  Medial longitudinal arch  Lateral longitudinal arch - smaller  Transverse arch

Talus – all of the body’s weight is transferred through this during single limb weight – bearing -no mm attachment; oddly shaped because it connects the leg to the foot -more than half of its surface is covered with articular cartilage *The medial posterior talus possesses a groove that is formed by the medial et lateral talar tubercles; running through this groove is the flexor halluces longus tendon Sinus tarsi – a depression; a channel that runs between the articulations of the talus et the calcaneus Calcaneus – largest et the strongest of the tarsal bone; 1st bones through which ground reaction forces are imparted during walking -transmits the majority of the body’s weight from talus to the ground Sustentaculum tali – a horizontal shelf on which the talus is supported; it supports the inferior medial aspect of the talus et where the 2 bones form 1 of their 3 articulations, the middle facet Navicular – boat-shaped bone; lies between the head of the talus et the 3 cuneiforms 3 Cuneiforms – lie across the instep of the foot to form the arched part o the dorsum of the foot known as the transverse arch of the foot  Medial cuneiform - largest  Intermediate - smallest  Lateral cuneiforms Cuboid – 6 sided bone Posterior side articulates with calcaneus Medial side articulates with lateral cuneiform Anterior side articulates with 4th et 5th metatarsals Its lateral et plantar surfaces contain a groove though which the peroneus longus tendon travels to the plantar foot. Metatarsal bones *Metatarsal et phalangeal bones comprise the forefoot 1st metatarsal – shortest but thickest 2nd metatarsal – thinnest et longest 4th metatarsal – positioned more posteriorly relative to the 3rd metatarsal 5th metatarsal – has a tuberosity on its lateral aspect et is the site of the insertion for the peroneus brevis tendon

*Immediately posterior to the first metatarsal head’s plantar surface are two small grooves within which two sesamoid bones are contained. Flexor hallucis longus tendon runs between them. Sesamoids serve to protect et guide the FHLT et protect the first metatarsal head by absorbing shock. Phalanges – 14 bones Great toe – has a proximal and a distal phalange Lateral toes – have proximal, middle et distal phalanges. Trochlear – heads of the proximal phalanges which fit into the bases of their adjacent phalanges

JOINTS 26 bones of the foot et ankle comprise 34 joints  Tibiofibular joints  Talocrural joints  Subtalar joints  Transverse tarsal joint o Talonavicular joint o Calcaneicuboid joint  Tarsometatarsal joints  Intermetatarsal joints  Metatarsophalangeal et Interphalangeal joints Dorsiflexion – occurs as the 2 segments of the joint move closer together. Plantarflexion – occurs when 2 segments move farther apart. Inversion – motion is a rotation movement so the bottom of the foot rolls to face the opposite limb. Eversion – opposite motion; plantar foot rolls laterally to face away from the opposite limb. Triplanar axis – a single joint axis that is not perpendicular to the cardinal planes but intersects all 3 planes Tibiofibular joints 2 joints that firmly hold tibia et fibula to each other:  Proximal tibiofibular joint  Distal tibiofibular joint Interosseous membrane – sheet of dense connective tissue, also runs between the 2 bones et assists in maintaining alignment of the 2 bones

Superior tibiofibular joint – described as “forgotten joint” *Because the tibial shaft is rotated laterally, the foot Is also laterally rotated in its alignment. This rotation creates an angle between the relative position of the knee et the position of the ankle. This angle is called Tibial torsion Arthrokinematics: The roll et glide of the fibula on the tibia occur in the same direction. The resting position for the joint is about 10deg of ankle plantarflexion. The closepacked position of the proximal tibiofemoral joint is full dorsiflexion Talocrural joint – commomnly referred to as ankle joint; between the talus et crus (a hinge joint with one degree of freedom of motion) Medial collateral ligament – also know as deltoid ligament; a large structure that has superficial et deep components -purpose is to restrict end range eversion or valgus tilting of the ankle Lateral collateral ligaments o the talocrural joint – not as strong as or as melded as those in the medial’s aspect. This ligaments include  anterior talofibular – flat band and weak; most often injured  posterior talofibular ligaments et the calcaneofibular ligament – stronger et thicker Arthrokinematics: When the joint moves in dorsiflexion, the talus abides by the convex – concave principle, so as it rolls anteriorly, it glides posteriorly. Subtalar joint – has 2 capsules 1.) encloses the posterior articular facets of the talus et calcaneus 2.) encloses the middle et anterior facets of the subtalar joint as well as the talonavicular joint cone – shaped sulcus (groove/trench) – runs between the posterior et middle articular surfaces of the talus to form the sinus tarsi sulcus or tarsal canal – runs from the sinus tarsi on the lateral ankle to the ankle’s medial side between the medial malleolus et sustentaculum tali et

separates the posterior et anterior capsules of the subtalar joint. Sinus tarsi – widest end of the sulcus et located just anterior to the lateral malleolus. *Interosseous ligament are the “proprioceptive subtalar center” responsible for the rapid reflex response to closed chain motion. Kinematics Subtalar joint does not move in a straight plane but produces movement on the axis that creates multiplanar motion. Although the subtalar joint has multiplanar movement, it is a uniaxial joint because pf the oblique alignment of its axis. Lateral ankle sprain – commonly affect the ankle joint proprioceptors Transverse tarsal joint – also known as the midtarsal joint or Chopart’s joint -formed by two articulating surfaces, the talonavicular et calcaneocuboid joints. Although they are 2 joint, they are still referred together as one. Talonavicular joint – has a rounded anterior talar head that fits into a concave navicular, nearly like a ball-and-socket joint The inferior aspect of this capsule is supported and reinforced by the spring ligament. Spring ligament – also known as the plantar calcaneonavicular ligament; a thick et inelastic triangular shaped ligament with a fibrocartilaginous lining of its surface adjacent to the talus. -its structure allows it to serve as a platform or hammock – like support for the head of the talus Calcaneocuboid joint – has its own capsule; wedge-like in its structure so little motion occurs between the joint segments. -this joint is a modified sellar, or saddle joint; primary supporting ligament of this joint is the plantar ligament which has 2 layers. Kinematics Transverse tarsal joint participates in movement of the forefoot on the hindfoot. It lowers the longitudinal arch of the foot during pronation et elevates the arch during supination. It also unlocks the foot to allow it to accommodate to the myriad surfaces the foot contacts et also absorbs the impact forces of weight-bearing during standing, walking,

running et jumping. It also locks the foot to convert it to a rigid lever for the transfer of forces required to propel the body forward or upward. Tarsometataral joints – link between the rearfoot et forefoot; they form the transverse metatarsal arch et provide some contribution to the longitudinal arch. -also called as Lisfranc’s joint 1st metatarsal joint – the largest of these joints et has its own capsule 2nd metatarsal – has the least amount f movement of the metatarsals, it is used as a reference point for the forefoot 4th et 5th metatarsals – most mobile Rays – are the functional unit of the forefoot. 1st ray – medial cuneiform et the 1st metatarsal 2nd ray – middle cuneiform et 2nd metatarsal 3rd ray – 3rd metatarsal et lateral cuneiform 4th ray – 4th metatarsal by itself 5th ray – includes only by the 5th metatarsal Intermetatarsal joints There are in fact, synovial joints between the 2nd et 3rd et between the 3rd et 4th metatarsal bases. Although there is no synovial joint between the 2st et 3nd metatarsal bases, there rare ligaments connecting the 2 structures Metatarsophalangeal et Interphalangeal joints – these corresponds in structure to those in the fingers, but they possess some functional differences; these joints are biaxial, moving in sagittal et transverse planes. -hyperextension is 90deg et flexion is only 30 to 45deg. The large range of hyperextension is required when standing on the toes et during walking in the late phase of stance after the heel comes off the ground. IP joint of toes are hinge joints with one degree of freedom; closed packed position when they are in full extension.

MUSCLES

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POSTERIOR GROUP OF MUSCLES:  SUPERFICIAL: o Gastrocnemius o Soleus o Plantaris

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Gastrocnemius O: LH: Lateral femoral condyle MH: posterior femoral surface I: Achilles tendon N: tibial portion of sciatic nerve A: PF, knee flexion - Makes up the major bulk of the calf mm Soleus O: posterior surface of fibula I: Achilles tendon N: tibial portion of sciatic nerve A: PF Plantaris O: Lat. Supracondylar line of femur I: Achilles tendon N: tibial portion of sciatic nerve A: weak assister of PF - Very small mm of superficial calf group; not consistently present - Fusiform fiber arrangement et very thin but long tendon; true purpose is unknown Function of the TRICEPS SURAE -aka three-headed mm of the calf -Gastrocnemius et Soleus (tendons of these 2 become the tendo calcaneus or Achilles tendon) -PF is performed mainly et exclusively by triceps surae. Mean value of the force exerted by triceps surae is equivalent to 2.4 times the body weight. Soleus - slow twitch mm fibers; concerned more with stabilization at ankle et control of postural sway; postural mm Gastrocnemius – fast twitch mm fibers et contains fast fatiguing motor units

DEEP: o FDL et FHL o Tibialis posterior Tom, Dick and Harry

Tibialis posterior O: post surf of interosseous membrane I: navicular tuberosity N: tibial nerve A: inversion et assist in PF - Deepest mm of the calf - Important mm to the dynamic function et control of the foot - Works throughout most of the time of weight – bearing in ambulation et has little time to rest Flexor digitorum longus O: tibia I: bases of the distal phalanges of 2nd – 5th toes N: tibial nerve A: flexion of MTP et IP joints, PF Flexor hallucis longus O: post surf on fibular et intermuscular septa I: base of distal phalanx of great toe N: tibial nerve A: flexion of 1st MTP, IP et PF - Strong mm LATERAL GROUP OF MUSCLES:  Peroneus longus  Peroneus brevis - These mm are also known as the fibularis longus et fibularis brevis Peroneus longus O: head of fibula I: base of 1st metatarsal N: superficial branch of common peroneal nerve A: eversion, PF - A direct continuation of biceps femoris; produces more torque Peroneus brevis O: Fibula I: styloid process of 5th metatarsal N: superficial branch of common peroneal nerve A: eversion, PF

ANTERIOR GROUP OF MUSLES  Tibialis anterior  EHL  EDL  Peroneus tertius - these mm are collectively referred to as pretibial muscles Tibialis Anterior O: Lat condyle of shaft of tibia I: base of the 1st metatarsal N: branch of CPN et branch of DPN A: DF - responsible for the roundness of the leg anteriorly - primary dorsiflexor of the ankle Extensor halluces longus (EHL) O: shaft of fibula et interosseous membrane I: base of distal phalanx of great toe N: branch of DPN A: extension of 1st MTP et IP joints, DF Extensor digitorum longus (EDL) and Peroneus tertius O: Tibia et fibula interosseous membrane I: base of middle et distal phalanges of 4 lesser toes N: branch of DPN A: extension of MTP et IP joints, DF, eversion - these mm are together because they are usually difficult to delineate from one another in their upper portion INTRINSIC MUSCLES OF THE FOOT (OINA at homework) -used mainly for stability or balance and for providing support et assistance to the foot during activity -play an important role in stability of the transverse tarsal arch and in fact a major contributor to the support of this arch Abductor hallucis – has major role in providing support to the medial longitudinal arch.

Arches of the foot Functions:  Allow the foot to adapt to various surfaces  Absorb the forces imparted to the foot during closed chain activities  Provide a weight bearing surface et BOS, change the foot to a rigid lever for propulsion of the body. Plantar aponeurosis – also referred to as plantar fascia; strong series of fascial bands that support the sole et sides of the foot from the calcaneal tuberosity to the toes; important to the integrity of all arches of the foot Windlass mechanism When the MTP joints hyperextend, the aponeurosis becomes taut as it wraps around the metatarsophalangeal joints, so the metatarsal bone et tarsal bone pull together et are converted into a rigid structure, causing the longitudinal arch to arise. The intrinsic et extrinsic mm contract concentrically to add an active force to the passive plantar fascia force, creating a higher arch. The windlass mechanism can be observed when the 1st MTP joint is passively positioned in hyperextension; the arches become rigid et the plantar aponeurosis becomes taut et easily palpated. Deformities of the foot Pes planus (Flat foot) – pronation of the foot in which the body weight acts to depress the medial longitudinal et transverse arches. Pes Cavus (Club foot) – high medial longitudinal arch that occurs with inversion of the calcaneus - extreme cases are known as Club foot Hallux Valgus – lateral deviation of the great toe at the MTP joint; this is often accompanied by inflammation of the bursa on the medial side of the toe joint; common cause of hallux valgus is the pes planus or overly pronated feet.