CHAPTER 11 Ankle and Foot

Bones Tibia Bears 90% of weight Is easily palpated tuberosity down anterior ridge Features the prominent medial malleolus

Bones Fibula Bears remaining 10% Prominent lateral malleolus

Bones Parts of the foot Rearfoot (tarsals) Midfoot (more tarsals) Talus and calcaneus Midfoot (more tarsals) Forefoot (metatarsals and phalanges)

Bones Three arches Medial longitudinal Lateral longitudinal Transverse

Bones Calcaneus Is largest and strongest tarsal bone Is first through which ground reaction forces are transmitted Transmits most of body weight from talus to ground

Bones Calcaneus Is protected by a thick fat pad Attaches to Achilles tendon on posterior aspect

Bones Metatarsals Metatarsals and phalanges comprise forefoot Numbered 1–5; medial to lateral Two sesamoids are just posterior to first metatarsal head on plantar surface.

Bones Phalanges 14 phalangeal bones 1: two 2–5: three each

Joints Motion terminology Dorsiflexion and plantarflexion Occur close to sagittal plane Inversion and eversion Occur in frontal plane Abduction and adduction Occur in transverse plane

Joints Motion terminology Pronation and supination Functional terms Motion occurs in three planes about an oblique axis with one degree of freedom. Terms are typically used in reference to the subtalar joint.

Motion terminology—pronation Joints Motion terminology—pronation Open kinematic chain, superior tibiofibular joint, and calcaneus on talus Dorsiflexion Abduction Eversion

Motion terminology—supination Joints Motion terminology—supination Open kinematic chain, superior tibiofibular joint, and calcaneus on talus Plantarflexion Adduction Inversion

Joints Talocrural Oblique hinge with one degree of freedom Medial collateral ligament = deltoid Lateral collateral ligament Anterior talofibular Calcaneofibular Posterior talofibular

Muscles Posterior group Superficial Gastrocnemius—two-headed, two-joint phasic muscle Soleus—tonic or slow-twitch, postural muscle Plantaris—very small, short muscle with long tendon

Muscles Posterior group Deep Tarsal tunnel Posterior tibialis—primary decelerator of pronation Flexor digitorum longus Flexor hallucis longus Tarsal tunnel

Muscles Lateral group Peroneus (fibularis) longus Has 2x larger in cross-sectional area compared with brevis Passes behind lateral malleolus, through a groove on cuboid, and onto base of first metatarsal Peroneus (fibularis) brevis Inserts into base of fifth metatarsal

Muscles Lateral group Function as primary everters of ankle and foot Innervated by superficial peroneal nerve

Muscles Anterior group Tibialis anterior Primary dorsiflexor of ankle Assists with controlling pronation Extensor hallucis longus—extend toes, evert ankle Extensor digitorum longus—extend toes Peroneus tertius

Function of Muscles and Joints Arches of the foot Functions: Allow foot to adapt to ground Absorb forces Provide a weight-bearing surface Assist and support foot during supination/pronation

Function of Muscles and Joints Loading of the foot Weight is distributed 50%–50% between calcaneus and metatarsal heads. During gait, heel and great toe experience greatest amount of force.