What common test is used to diagnose lateral epicondylitis?

The Mills Test is specifically designed to assess for lateral epicondylitis, often referred to as "tennis elbow." This condition involves the inflammation of the tendons that attach to the lateral epicondyle of the humerus, typically due to overuse or repetitive motions of the forearm.

During the Mills Test, the examiner stabilizes the elbow and extends the wrist while the patient keeps the forearm in a neutral position. If this maneuver elicits pain over the lateral epicondyle, it is indicative of lateral epicondylitis.

The other tests mentioned do not specifically assess for this condition. The Thompson Test is used to evaluate the achilles tendon for rupture, the Valgus Stress Test assesses for medial collateral ligament injuries in the knee, and the Finkelstein Test is used to diagnose De Quervain's tenosynovitis, affecting the tendons of the thumb. Hence, the Mills Test is the correct choice for diagnosing lateral epicondylitis.