The ankle joint is another example of a hinge joint, formed by the articulation of the medial malleolus of the tibia, the lateral malleolus of the fibula and the trochlea of the talus. The articulating surfaces of these bones are covered with cartilage to prevent movement induced erosion. The anterior end of the talus is wider than its posterior end, which allows for increased stability of the ankle when it’s dorsiflexed (the most stable configuration).
Movements of the ankle
The ankle plays a major role in movement and in lower limb stability. Being a hinge joint, the ankle is capable of 2 types of movement:
1. Dorsiflexion: this movement is equivalent to extension, permitting the foot to be raised upward 10-30°. All muscles whose tendons pass into the foot anterior to the ankle joint assist with dorsiflexion (see anterior compartment of the leg).
2. Plantarflexion: causes the foot to point downwards between the ranges of 20-50°. All muscles whose tendons pass into the foot posterior to the ankle joint and those whose tendons attach to the calcaneus aid with this movement (see posterior compartment of the leg).
The anterior and posterior tibiofibular ligaments and the thick lower portion of the interosseous membrane tightly bind the distal tibia and fibula together providing mechanical stability to these joints during these movements.
Ligaments of the ankle joint
Similar to the knee, the ankle joint is reinforced by collateral ligaments at its sides.
· Deltoid ligament: this triangular ligament binds the medial malleolus to the tarsal bones (navicular, calcaneus and talus) on the medial side of the joint.
· Lateral ligament: is the collateral ligament on the lateral side of the ankle joint. It’s made up of 3 separate ligaments (talofibular anterior and posterior and calcaneofibular) which bind the lateral malleolus of the fibula to the tarsal bones.