Radioscaphocapitate ligament

The radioscaphocapitate (RSC) ligament is one of the palmar (volar) extrinsic radiocarpal ligaments and is among the strongest stabilizing ligaments of the wrist.

It originates from the radial styloid process at the volar tip of the radius and courses distally and ulnarly, crossing the palmar aspect of the scaphoid waist, before inserting into the volar capitate. Along its course it forms a hemicircumferential sling around the distal pole of the scaphoid and interdigitates with fibers from the palmar triangular fibrocartilage complex just palmar to the capitate head, with only a minor direct insertion into the body of the capitate.

• Part of the palmar radiocarpal ligament complex, together with the long radiolunate, radioscapholunate, and short radiolunate ligaments. It is intracapsular, enveloped by a superficial fibrous stratum and a deep synovial stratum. [

• Relationship to the long radiolunate ligament: The RSC lies radial to the long radiolunate ligament, from which it is separated along its course by a space called the interligamentous sulcus — a normal finding on MRI that should not be mistaken for a tear (the two may occasionally appear as a single broad band).

• Function: It provides radial-sided radiocarpal stability, acts as a volar sling supporting and stabilizing the volar-flexed scaphoid waist, and serves as a secondary restraint to scaphoid–lunate motion. Together with the long radiolunate ligament, it is a principal restraint against carpal ulnar translation and dynamic radiocarpal instability.

• Imaging: It is well seen as a hypointense band on MR arthrography (best in the transverse plane) and can appear as a volar filling defect during radiocarpal arthrography.