There are two flexor retinacula in the body. One flexor retinaculum is present in the wrist and other is present in the ankle.
Flexor Retinaculum of Wrist
The flexor retinaculum of the wrist is also called transverse carpal ligament or anterior annular ligament.
It is a strong, fibrous band, that arches over the carpus, converting the deep groove on the front of the carpal bones into a tunnel, the carpal tunnel.
Flexor Retinaculum of The Foot
It is also known as laciniate ligament or internal annular ligament.
It extends from the tibial malleolus above to the margin of the calcaneus below, converting a series of bony grooves in this situation into canals for the passage of the tendons of the Flexor muscles and the posterior tibial vessels and tibial nerve into the sole of the foot.
In a similarity to its counterpart in the hand, it is continuous in upper part with the deep fascia of the leg, and with the plantar aponeurosis below.
It contains, from the medial side to lateral, the tendon of the tibialis posterior, the tendon of the flexor digitorum longus; the posterior tibial vessels and tibial nerve and the tendon of the Flexor hallucis longus.