The flexor retinaculum is a strong, square-shaped fibrous band that crosses the carpal bones transversely to form the roof of the fibro-osseous carpal tunnel. It attaches to the hamulus of the hamate and the pisiform bone on the ulnar side of the wrist and forms two laminae laterally, a superficial lamina attaches to the tubercles of the scaphoid and trapezium and a deep lamina attaches to the trapezium. In addition to forming the strong retinacular band for the digital flexor tendons, it provides attachment for the palmaris longus and flexor carpi ulnaris, while the flexor carpi radialis passes between the two laminae on the lateral side. At its distal border some of the intrinsic muscles of the hand arise from its superficial surface.

Retinaculum musculorum flexorum manus