Finkelstein's Test is primarily used for diagnosing which condition?

Finkelstein's Test is specifically designed to assess for De Quervain's tenosynovitis, which is characterized by inflammation of the tendons that control thumb movement. During the test, the patient makes a fist with the thumb tucked inside the fingers while the clinician stabilizes the forearm and then gently deviates the wrist toward the ulnar side. A positive test is indicated by pain over the radial side of the wrist, which confirms irritation of the abductor pollicis longus and extensor pollicis brevis tendons.

The unique positioning and movement involved in Finkelstein's Test directly target the specific tendons and their surrounding tissue affected by De Quervain's. This makes it a reliable and effective diagnostic tool to identify this condition. The other options involve different anatomical structures and mechanisms, thus falling outside the specific purpose of this test.