Ulnocapitate ligament

The ulnocapitate ligament is one of the four extrinsic components of the palmar ulnocarpal ligamentous complex (UCLC) — alongside the ulnolunate, ulnotriquetral an ulnopisiform ligaments.

Origin and course

It is the only ulnocarpal ligament that attaches directly to the ulnar head. It originates at the fovea of the ulnar head, near the attachments of the volar and dorsal radioulnar ligaments, and runs superficial to the ulnolunate and ulnotriquetral ligaments, reinforcing the palmar component of the lunotriquetral interosseous ligament along its course.

Insertion

It connects the ulnar fovea to the body of the capitate, and distally interdigitates with fibers of the radioscaphocapitate ligament and the scaphotriquetral ligament, together forming the palmar arcuate (greater arc) ligament.

Relationship to the TFCC

Unlike the ulnotriquetral and ulnolunate ligaments, its origin lies at the palmar fovea rather than on the ulnar styloid — so it attaches to the fovea region of the ulnar head rather than directly to the TFCC disc itself. The three ligaments of the UCLC are described as macroscopically confluent and indistinguishable from each other in most specimens, and merge firmly with the palmar radioulnar ligament.

Imaging On ultrasound, it can be visualized with the transducer at the volar-ulnar wrist, angled slightly radially toward the capitate, appearing as an echogenic, fibrillary band crossing the lunotriquetral joint; it is difficult to appreciate reliably on MRI even with correct anatomic orientation.