Palmar radioulnar ligament

The palmar (volar) radioulnar ligament (PRUL) is one of the two radioulnar ligaments that, together with the central articular disc, form the ligamentous core of the triangular fibrocartilage complex (TFCC) and serve as the principal stabilizers of the distal radioulnar joint (DRUJ). It is an intracapsular structure that arises from the palmar rim/margin of the sigmoid notch of the distal radius and passes ulnarly to insert on the distal ulna, enclosing the palmar edge of the articular disc.

Biomechanical role. The divergent superficial and deep insertions allow smooth tension transfer during pronation–supination, preserving DRUJ stability while permitting full forearm rotation. The PRUL is the principal restraint against dorsal translation of the distal ulna relative to the radius, and it provides secondary restraint (with the interosseous membrane) against palmar translation. It elongates and tightens maximally in supination and becomes progressively lax in pronation. Because it lengthens under axial load in the extended wrist, it is vulnerable to tearing during a fall on an outstretched hand. The PRUL also serves as the attachment site for the ulnocarpal (ulnolunate and ulnotriquetral) ligaments, which anchor to it rather than directly to the ulna, thereby linking DRUJ and ulnocarpal joint stability.