The quadrate ligament, or ligament of Denucé, is one of the ligaments of the proximal radioulnar joint in the upper forearm.
The proximal radioulnar joint viewed from above. The quadrate ligament is seen attached to the dislodged radius cut just above the neck.
The quadrate ligament is a fibrous band attached to the inferior border of the radial notch on the ulna and to the neck of the radius. Its borders are strengthened by fibers from the upper border of the anular ligament. The ligament is 11 mm (0.43 in) long, 8 mm (0.31 in) wide, and 1 mm (0.039 in) thick.
The quadrate ligament reinforces the inferior part of the capsule of the elbow joint and contributes to joint stability by securing the proximal radius against the radial notch and by restricting excessive supination (10–20° restriction) and, to a lesser degree, pronation (5–8°).