Subtalar joint, also known as talocalcaneal joint, is the posterior joint between the talus and the calcaneum. It is a plane synovial joint that allows movements of inversion and eversion of foot.
Articular surfaces of subtalar joint:
The articulation takes place between the inferior surface of body of talus and the facet on the middle of the upper surface of calcaneum. As this is a synovial joint, the articular surfaces are covered with hyaline cartilage.
Capsule of subtalar joint:
The capsule encloses the joint completely. It is attached to the margins of the articular surfaces of the two bones.
Ligaments of subtalar joint:
There are four important ligaments associated with this joint. They are discussed below.
- Lateral talocalcaneal ligament: This ligament is a short, flat fasciculus that descends obliquely back from the lateral talar process to the lateral calcaneal surface. It is attached anterior and superior to the calcaneofibular ligament of ankle joint.
- Medial talocalcaneal ligament: It connects the medial talar tubercle to the back of the sustentaculum tali and medial surface of calcaneum.
- Interosseous talocalcaneal ligament: It is a broad, flat band in the sinus tarsi. The posterior part of this ligament is associated with the talocalcaneal joint. It is considered to be taut in eversion.
- Cervical ligament: It lies just lateral to the tarsal sinus and is attached to the superior calcaneal surface. It is considered to be taut in inversion of foot.
Synovial membrane of subtalar joint:
The synovial membrane of this joint is separate from other tarsal joints, however, direct communication with the ankle joint may occur.
Nerve supply to subtalar joint:
This joint is innervated by branches of the posterior tibial, medial plantar and sural nerves.
Movements of subtalar joint:
Inversion and eversion of foot are two important movements occurring at this joint.
- Inversion of foot: It is the movement in which the sole of foot faces medially. It is performed by tibialis anterior, tibialis posterior and gastrocnemius-soleus complex.
- Eversion of foot: It is the movement of the foot in which its sole faces laterally. It is performed by peroneus longus, peroneus tertius and peroneus brevis.