Inferior extensor retinaculum of foot

The inferior extensor retinaculum of the foot (cruciate crural ligament, lower part of anterior annular ligament) is a Y-shaped band placed in front of the ankle-joint, the stem of the Y being attached laterally to the upper surface of the calcaneus, in front of the depression for the interosseous talocalcanean ligament; it is directed medialward as a double layer, one lamina passing in front of, and the other behind, the tendons of the Peronæus tertius and Extensor digitorum longus.

At the medial border of the latter tendon these two layers join together, forming a compartment in which the tendons are enclosed.

From the medial extremity of this sheath the two limbs of the Y diverge: one is directed upward and medialward, to be attached to the tibial malleolus, passing over the Extensor hallucis longus and the vessels and nerves, but enclosing the Tibialis anterior by a splitting of its fibers.

The other limb extends downward and medialward, to be attached to the border of the plantar aponeurosis, and passes over the tendons of the Extensor hallucis longus and Tibialis anterior and also the vessels and nerves.