Ankle and foot


ESS 303 – Biomechanics

Ankle and Foot

Tibiofibular Joint

 Similar to radioulnar joint

 Superior tibiofibular joint

 Middle tibiofibular joint (interosseus membrane)

 Inferior tibiofibular joint

 Rotational movements not called pronation or supination

Ankle Joint

 Distal tibia and fibula articulates with talus

 Hinge joint – sagital plane

 Flexion – dorsiflexion (about 20°)

 Extension – plantarflexion or volar flexion (30-50°)

 Some transverse plane (rotational) movement possible

 7 ° medial, 10 ° lateral

 Some frontal plane (side-to-side tilt) movement possible

 ≈ 5 ° frontal talar tilt

Foot Positions

 Subtalar or talocalcaneal joint

 Inversion & eversion

 Pronation = ankle dorsiflexion + subtalar (calcaneal) eversion + forefoot abduction (external rotation)

 Supination = ankle plantarflexion + subtalar (calcaneal) inversion + forefoot adduction (internal rotation)

Foot Positions

Arches of the Foot

Arches of the Foot

Arch Positions

 Normal

 High arch: Pes cavus

 Low arch (flat foot): Pes planus

Ankle Joint Stability

 Distal ends of tibia and fibula – like mortise (pinchers) of adjustable wrench

 Tibia is weight bearing

 Fibula is considered non-weight bearing

– may hold up-to 10% of body weight

 Multiple ligaments

Ligaments and Sprains

Ligaments and Sprains

Return to Activity

 Must have complete range of motion and at least 80-90% of pre-injury strength before return to sport

 If full practice is tolerated w/out insult, athlete can return to competition

 Must involve gradual progression of functional activities, slowly increasing stress on injured structure

Movements & Major Muscles

 Dorsiflexion: Tibialis anterior

 Plantar flexion: Gastrocnemius & soleus

 Inversion: Tibialis anterior, peroneus longus & peroneus brevis

 Eversion: Peroneus tertius

Biomechanics of Gate

 Stance phase (60-65%)

 Heel contact (heel strike or initial contact)

 Foot flat (loading response)

 Mid stance

 Heel off (terminal stance)

 Toe off

 Swing phase (35-40%)

 Toe off (acceleration or initial swing)

 Mid swing

 Heel contact (deceleration or terminal swing)

Single Limb Weight Bearing

 Pelvis forms a 1st class lever

 Hip is fulcrum, resistance force is body weight, effort force is from abductors and adductors

 Body is drawn over supporting leg by adductor muscles

 Hip abductors of the support leg prevent the pelvis from dropping on the opposite

(unsupported) side

Knee Joint and Gate

Knee Joint and Gate

 Chimpanzee: medial and lateral condyle similar

 Human: medial condyle larger than lateral condyle – allows

COM to shift over foot

Advantages/disadvantages to Bipedal


 Disadvantages

 Loss of speed

 Loss of agility

 Advantages

 Carry food

 Carry tools

 Increased ability to nurture/protect offspring

 Enable to give birth more often