Labral tears and acromioclavicular joint abnormalities were differentiated on physical examination using a new diagnostic test. The standing patient forward flexed the arm to 90 degrees with the elbow in full extension and then adducted the arm 10 degrees to 15 degrees medial to the sagittal plane of the body and internally rotated it so that the thumb pointed downward. The examiner, standing behind the patient, applied a uniform downward force to the arm. With the arm in the same position, the palm was then fully supinated and the maneuver was repeated. The test was considered positive if pain was elicited during the first maneuver, and was reduced or eliminated with the second. Pain localized to the acromioclavicular joint or "on top" was diagnostic of acromioclavicular joint abnormality, whereas pain or painful clicking described as "inside" the shoulder was considered indicative of labral abnormality. A prospective study was performed on 318 patients to determine the sensitivity, specificity, and positive and negative predictive values of the test. Fifty-three of 56 patients whose preoperative examinations indicated a labral tear had confirmed labral tears that were repaired at surgery. Fifty-five of 62 patients who had pain in the acromioclavicular joint and whose preoperative examinations indicated abnormalities in the joint had positive clinical, operative, or radiographic evidence of acromioclavicular injury. There were no false-negative results in either group.