Stability of the ankle mortise relies on the configuration of the osseus structures and the ligaments.
The main articulation is between the talus and the tibial plafond. The saddle-shaped dome of the talus fits exactly into the tibial plafond and small disturbances in the congruity of this tibiotalar joint reduce the contact area and will overload the articular cartilage leading to arthrosis.
On the medial side the talotibial joint is firmly supported by the medial malleolus and the medial collateral ligament, which is stronger than its lateral counterpart. On the lateral side there is a flexible support by the lateral complex which consists of fibula, syndesmosis and lateral collateral bands.
The syndesmosis is the fibrous connection between the fibula and tibia formed by the anterior and posterior tibiofibular ligament located at the level of the tibial plafond (French for ceiling) and the interosseus ligament which is the thickened lower portion of the interosseus membrane and is located 2cm above the tibial plafond where the superior recess of the joint ends.
The anterior and posterior tibiofibular ligaments are often referred to as anterior and posterior syndesmosis.
The lateral collateral ligaments connect the distal fibula to the talus and calcaneus. The flexibility of the lateral complex allows talus and fibula to rotate and translate during normal ankle movements. This fibular motion at the syndesmosis is an essential part of the normal ankle function.
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