O’Brien’s Test assesses the glenoid labrum and AC joint. Ask the patient to raise her arm to 90 degrees of flexion with her elbow extended. Adduct her arm 10 to 15 degrees, to approximately midline, then internally rotate the arm and apply a downward force. Repeat the test with the arm externally rotated. The test is positive for labral pathology if pain is produced with the arm internally rotated but not externally rotated. The test is positive for AC joint pathology if there is pain with both maneuvers localized to the AC joint.