The ankle is made up of 4 distinct bones, the tibia, fibula, talus and calcaneus. The interaction between these bones allows for movement of the joint in certain directions. In turn, the ankle is made up of 3 separate joints:
- Talocrural Joint: This is a hinge joint formed by the distal ends of the fibula and tibula that enclose the upper surface of the talus. It allows for both dorsiflexion (decreasing the angle between the foot and the shin) and plantarflexion (increasing the angle).
- Inferior Tibiofibular Joint: This is a strong joint between the lower surfaces of the tibia and fibula. This is supported by the inferior tibiofibular ligament.
- Subtalar Joint: This joint comprises the articulating surfaces of the talus and the calcaneus. It provides shock absorption and the movements of inversion and eversion (inward and outward ankle movements respectively) occur here.
The ligaments of the ankle joint are comprised mainly of the collateral ligaments, both medial (inner) and lateral (outer). These are extremely important in the stability of the ankle itself.
Lateral Collateral Ligament
The lateral collateral ligament prevents excessive inversion. It is considerably weaker than the larger medial ligament and thus sprains to the lateral ligament are much more common. It is made up of 3 individual bands:
Anterior talofibular ligament (AFTL): passes from the fibula to the front of the talus bone.
Calcaneofibular ligament (CFL)- connects the calcaneus and the fibula
Posterior talofibular Ligament (PTFL)- passes from the back of the fibula to the rear surface of the calcaneus.
Medial Collateral Ligament
The medial ligament (also known as the deltoid ligament) is considerably thicker than the lateral ligament and spreads out in a fan shape to cover the distal (bottom) end of the tibia and the inner surfaces of the talus, navicular, and calcaneus.