Flexor retinaculum of the hand Flexor retinaculum of the hand The flexor retinaculum (transverse carpal ligament, or anterior annular ligament) is a fibrous band on the palmar side of the hand near the wrist. It arches over the carpal bones of the hands, covering them and forming the carpal tunnel. The flexor retinaculum is a strong, fibrous band that covers the carpal bones on the palmar side of the hand near the wrist. It attaches to the bones near the radius and ulna. On the ulnar side, the flexor retinaculum attaches to the pisiform bone and the hook of the hamate bone. On the radial
Hamate bone bone has six surfaces: The "hook of hamate" () is found at the proximal, ulnar side of the hamate bone. The hook is a curved, hook-like process that projects 1–2 mm distally and radially. The hook forms the ulnar border of the carpal tunnel, and the radial border for Guyon's canal. Numerous structures attach to it, including ligaments from the pisiform, the transverse carpal ligament, and the tendon of Flexor carpi ulnaris. Its medial surface to the flexor digiti minimi brevis and opponens digiti minimi; its lateral side is grooved for the passage of the flexor tendons into the palm