To perform the test, the examiner grasps the wrist with their thumb over the patient's 2nd metacarpal in order to prevent the scaphoid from moving into its more vertically oriented position in radial deviation. For the test, the wrist needs to be in slight extension.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 if the test is positive. For completeness, the test must be performed to both wrists for comparison. If the scapholunate ligament is disrupted, the scaphoid will subluxate over the dorsal lip of the distal radius.
Watson's test is used by physicians to diagnose scapholunate instability. This test has a low specificity and sometimes is positive for capito-lunate instability. As many as 20% of normal wrists will also have a 'clunk'.