From a functional point of view considered as a hinge or ginglymus joint.
Fibrous capsule surrounds joint – thinner anteriorly and posteriorly.
Also called medial collateral ligament – strong triangular band – has deep and superficial components – 4 bands:
Superficial tibionavicular, tibiocalcaneal, posterior tibiotalar ligaments
Deep anterior tibiotalar ligament
Anterior talofibular ligament:
From anterior surface of the tip of the lateral malleolus to neck of talus
From tip of lateral malleolus tubercle on lateral aspect of calcaneus
Posterior talofibular ligament:
From posterior surface of lateral malleolus posterior process of talus
Function of ankle joint:
Axis – generally considered as being, on average, 8 degrees from transverse plane and 20-30 degrees from frontal plane – directed laterally, posteriorly and plantarly – clinical approximation is imaginary line between distal tips of malleoli – BUT axis moves during plantarflexion and dorsiflexion.
As foot dorsiflexes the fibula moves proximally due to oblique angle of tibiofibular interosseous ligament (restriction in motion at tibiofibular joints may limit ankle joint range of motion).
Open kinetic chain motion – abduction and dorsiflexion – abduction and plantarflexion
Range of motion – generally considered that for normal function the foot must be able to dorsiflex on the foot at least 10 degrees from a right angle with the leg.
Ball and socket ankle joint:
Rare. Trochlea surface of talus is hemispherical – permits inversion and eversion of ankle joint as well as dorsiflexion and plantarflexion. Usually asymptomatic.
A variation of the true ‘ball and socket’ ankle joint may occur due to large individual variations in ankle joint axis position in those who adapt to a limited range of motion at the subtalar joint.