Finkelstein’s test is a test for De Quervain’s Tenosynovitis, which is an inflammation of the tendons of two muscles, Abductor Pollicis Longus, and Extensor Pollicis Brevis.
To perform the test, have your client make a light fist with their thumb inside their fingers. Have one hand holding just proximal to the wrist, then gently deviate the wrist to the ulnar side with your other hand. Pain felt over the distal radius may be from inflammation of the tendons going to the thumb.
This test may also be positive if there is a restriction of the Radial nerve.