Fascia · Hand

Extensor retinaculum

Retinaculum musculorum extensorum manus

An oblique band roughly two fingers wide across the back of the wrist, strapping the extensor tendons down against the carpus. It anchors to the anterolateral border of the lower radius on the thumb side and crosses obliquely to the pisiform and triquetrum on the little-finger side — deliberately skipping the ulna, so the forearm can still rotate underneath it. Septa run from its deep surface down to ridges on the radius and the carpus, dividing the space beneath into six separate tunnels, each carrying one group of extensor tendons in its own sheath. Without it those tendons would lift away from the wrist like bowstrings every time the fingers straightened.