Subtalar joint

The subtalar joint (Talocalcaneal joint) is the articulation between the talus and calcaneus bones in the foot, located just below the ankle joint.

The subtalar joint is often described as two separate joints: the anterior subtalar joint and the posterior subtalar joint, which are separated by the tarsal canal and sinus tarsi. These two compartments do not communicate and have distinct articular surfaces and capsules. This joint is also referred to as the "anatomical subtalar joint" or "subtalar joint proper". However, in clinical practice, the subtalar joint is considered as a functional unit consisting of the anatomical subtalar joint and talocalcaneonavicular joint, termed as "clinical subtalar joint".

As a confusion factor, some authors describe three articulations between talus and calcaneus for the anatomical subtalar joint but that in fact correspond to the three talar articular facets of calcaneus :

• Anterior: head of talus with anterior facet of the calcaneus; small articulation in size, just lateral to medial facet

• Middle: the medial (sustentacular) facet of talus with the middle facet at the sustentaculum tali of the calcaneus

• Posterior: posterior facet of the talus with posterior facet of the calcaneus; largest articulation in size

The subtalar joint allows for inversion and eversion movements of the foot, which are essential for adapting to uneven surfaces and for normal gait biomechanics. Its axis of rotation is complex and not fixed, with instantaneous axes that change orientation during movement, contributing to its multiaxial nature.

The subtalar joint is stabilized by several ligaments:

• Lateral talocalcaneal ligament

• Medial talocalcaneal ligament

• Posterior talocalcaneal ligament

• Talocalcaneal interosseous ligament

• Anterior talocalcaneal ligament