Corpus: Inferior extensor retinaculum of foot

The inferior extensor retinaculum of the foot is a Y-shaped ligament, located in the area of the ankle. It tightens the extensor tendons of the lower leg muscles.

The broad base of the inferior extensor retinaculum originates on the cranial surface of the calcaneus, just in front of the depression for the interosseous talocalcaneal ligament. From this point, it extends medially in two layers of fibers, with one layer running in front of and the other behind the tendons of the third fibular muscle and the long extensor muscle of the toes.

Further medially, these two layers rejoin to form a tendon compartment for the enclosed tendons. The ligament then divides into two branches, forming a Y-shape.

The cranial branch of the Y runs obliquely proximally and medially, attaching to the medial malleolus. It passes over the tendon of the extensor hallucis longus muscle and encompasses the tendon of the anterior tibial muscle within its fibers.

The caudal branch of the Y extends downward and medially, attaching to the edge of the plantar aponeurosis. It passes over the tendons of the extensor hallucis longus muscle and the anterior tibial muscle.

The inferior extensor retinaculum holds the extensor tendons in place at the back of the foot during extension. Along with the superior extensor retinaculum, it redirects the force vector of the extensor tendons toward the foot.