The human ankle joint is a connection between the foot and lower leg. It is divided into the upper ankle joint (tibiotarsal articulation) and lower ankle joint (talotarsal articulation).
The upper ankle joint is a hinge joint. Its main task is to enable dorsiflexion (stretching) and plantar flexion (bending). The upper ankle joint is composed of the three bones:
The tibia and fibula form the so-called “ankle mortise” which consists of the medial and lateral malleoli. In the distal end of the ankle mortise sits the trochlea tali, the upper surface of the talus. This allows the articular surfaces to glide upon each other and assures the cartilage surfaces to move freely. The bony anatomy of the lower ankle joint (LAJ) is less complex as it basically consists of two parts. The following bones form the lower ankle joint:
The front part of the lower ankle joint (talocalcaneonavicular articulation) is an articulation between talus, calcaneus and navicular bone. The back part of the lower ankle joint is an articulation between talus and calcaneus and is called subtalar joint. The lower ankle joint permits two movements: pronation and supination of the foot – due to the fact that the axis enabling the pro- and supination stands at an 30° to 40° degree angle to the vertical leg axis.
The anatomy of the numerous ligaments of the ankle joint is quite interesting. For example the syndesmosis is a common localization for injuries. The syndesmosis ligaments consist of the anterior talofibular ligament on the ventral part and the posterior talofibular ligament on the dorsal part of the distal lower leg.
An important ligament at the ankle joint is the deltoid ligament which is composed of the tibiocalcaneal, tibionavicular and tibiotalar part. It is located at the medial side of the ankle joint. On the lateral side is the fibular collateral ligament (or lateral collateral ligament, LCL). This ligament plays a major role in the restriction of supination in the lower ankle joint. A supination trauma (spraining one’s ankle) is often caused by overstretching or complete rupture.