Watson's test is a diagnostic test of the wrist for scapho-lunate instability. To perform the test, the examiner grasps the wrist with their thumb over the patient's scaphoid tuberosity. The patient's wrist is then moved from ulnar to radial deviation. The examiner will feel a significant 'clunk' and the patient will experience pain (even on the normal side). For completeness, the test must be performed to both wrists.
If the scapho-lunate ligament is disrupted, the scaphoid will tend to turn down and the lunate to turn up. This procedure reproduces the subluxation.