Hand Orthopedics Ulnar Instability Criteria Calculator

About ulnar-sided wrist instability (DRUJ / TFCC)

When the ulnar side of the wrist becomes unstable, the problem usually sits at the distal radioulnar joint (DRUJ) and the triangular fibrocartilage complex (TFCC), which is the main stabilizer there. The TFCC cushions the ulnar carpus and ties the radius and ulna together, and its deep foveal fibers are what hold the DRUJ steady. An injury here may be traumatic, often a fall or a forced twist, or it may be degenerative, tied to ulnar impaction and positive ulnar variance. What patients report is pain on the ulnar side, clicking, and weakness or pain when they rotate the forearm, which gets worse under load.

Clinical criteria and how it is assessed

You get to the diagnosis by pairing a focused exam with imaging. The findings this calculator draws on include:

• DRUJ ballottement test: if the ulnar head slides too far volar-to-dorsal against the radius compared with the healthy side, the joint is unstable.
• Positive ulnar fovea sign: tenderness in the soft spot between the ulnar styloid and the flexor carpi ulnaris, which points toward a foveal TFCC tear.
• Ulnocarpal stress (grind) test and dynamic provocation that bring the ulnar pain back.
• Palmer classification, which sorts TFCC tears into traumatic (class 1: A central, B ulnar/distal, C ulnocarpal, D radial avulsion) and degenerative (class 2) lesions.
• Deep foveal disruptions tend to leave the DRUJ unstable, while peripheral ligament injuries can keep it stable. MRI, and sometimes arthroscopy, confirms the lesion.

Who uses this

Hand and orthopedic surgeons lean on these criteria, along with sports medicine physicians, residents, hand therapists and physiotherapists. They use them to pin down where the ulnar wrist pain is coming from, gauge whether the DRUJ is stable, and choose between conservative care and repair.

FAQ

What does a positive ballottement test mean? When the ulnar head moves too much front-to-back on the radius, the DRUJ is probably unstable.

What is the TFCC? It is the triangular fibrocartilage complex, a structure of cartilage and ligaments on the ulnar wrist that keeps the DRUJ stable and supports the carpus.

This tool is educational only and does not replace a medical evaluation. If ulnar wrist pain or instability sticks around, have a qualified clinician assess it, image it and manage it.