Beyond Tennis Elbow: The Radiocapitellar Joint as an Unfamiliar Source of Lateral Elbow Pain. A Case Report

BACKGROUND: Nontraumatic lateral elbow pain is most often the result of lateral epicondylitis commonly called “tennis elbow,” most often from repetitive motion from occupational or sports activities. Lateral elbow pain may also come from pain from the radiocapitellar joint of the elbow. The radiocapitellar joint is part of the proximal radioulnar joint, which is responsible for pronation and supination of the forearm. We describe a case of a person who was first misdiagnosed with tennis elbow but instead had radiocapitellar pain. CASE PRESENTATION: The case included a history of pain primarily when lifting with the forearm pronated but not supinated, reproduction of the exact “same: pain with radiocapitellar joint palpation, and a negative radiocapitellar impingement test. The initial numeric pain-rating scale (NPRS) score of pain was a 7/10 with activity, the QuickDASH (shortened version of the Disabilities of the Arm, Shoulder and Hand outcome measure) score was 52, and manual muscle testing showed significant weakness of the pronator teres muscle (Fair-plus muscle grade). OUTCOME: Successful intervention included a progressive strengthening program for the pronator teres muscles of the forearm. NPRS reduced from 7/10 to 0/10; QuickDASH reduced from 52 to 0. DISCUSSION: Therapists should include radiocapitellar joint pain as a differential diagnosis when patients come in with lateral elbow pain. JOSPT Cases 2026;6(1):32-36. Epub 8 January 2026. doi:10.2519/josptcases.2026.0197