Each wrist and ankle of the human body contains a structure called the flexor retinaculum. A flexor retinaculum consists of a fibrous band of fascia, which is a sheet of dense connective tissue that covers or binds other body structures. The flexor retinaculum of the foot, also known as the laciniate ligament, covers the tendons of the flexor muscles of the ankle.
The specific tendons covered are the tibialis posterior, flexor digitorum longus, and flexor hallucis longus, which all help to flex the foot so that the toes point downward. The function of the flexor retinaculum of the foot is to prevent subluxation, or partial dislocation, of these tendons.
The flexor retinaculum of the foot also covers the posterior tibial artery and vein and the tibial nerve. Each of these structures comes from the posterior (back) compartment of the leg, through the ankle, and into the sole of the foot. They pass through the flexor retinaculum immediately posterior to (behind) the medial malleolus, which is the network of nerve tissue and muscle that surrounds the ankle joint.