What These Shoulder Tests Assess
These are physical examination maneuvers that assess different components of the rotator cuff and shoulder labrum: the Empty Can (Jobe) Test evaluates the supraspinatus, the Cross-Arm Test assesses the acromioclavicular joint, the Lift-Off Test examines the subscapularis, and O'Brien's Test detects superior labral anterior-posterior (SLAP) lesions.
Empty Can (Jobe) Test
- Target Structure: Supraspinatus muscle (superior rotator cuff)
- Technique: Patient elevates arms to 90° in the scapular plane with thumbs pointing down (as if emptying a can), examiner applies downward resistance
- Positive Finding: Pain or weakness indicates supraspinatus pathology
Important caveat: Recent biomechanical modeling demonstrates that both the Jobe (Empty Can) and Full-Can tests have low biomechanical sensitivity for detecting superior rotator cuff tears, as supraspinatus activity is more than twofold lower than lateral deltoid activity during these maneuvers 1. The deltoid can compensate significantly, potentially masking tears.
Cross-Arm (Cross Body Adduction) Test
- Target Structure: Acromioclavicular (AC) joint
- Technique: Patient horizontally adducts the arm across the body
- Positive Finding: Pain localized to the AC joint indicates AC joint pathology
This test showed 77% sensitivity for isolated chronic AC joint lesions, though specificity was lower 2. When combined with other AC joint tests, diagnostic accuracy improves substantially. The test is more useful for ruling out AC pathology (negative predictive value >94%) than confirming it (positive predictive value <30%) 2.
Lift-Off Test
- Target Structure: Subscapularis muscle (anterior rotator cuff)
- Technique: Patient places hand behind back at waist level and attempts to lift hand away from body against resistance
- Positive Finding: Inability to lift hand off back or weakness indicates subscapularis tear
This is the superior test for subscapularis integrity. Biomechanical analysis confirms the Lift-Off test generates significantly higher subscapularis activity compared to the alternative Bear Hug test (P < .001) 1, making it more sensitive for detecting subscapularis tears.
O'Brien's (Active Compression) Test
- Target Structure: Superior labrum (SLAP lesions) and AC joint
- Technique: Patient forward flexes arm to 90° with elbow extended, then adducts 10-15° medially and internally rotates (thumb down). Examiner applies downward force. Test repeated with arm supinated (thumb up)
- Positive Finding: Pain with thumb down that decreases with thumb up suggests SLAP lesion; pain localized to AC joint in both positions suggests AC pathology
O'Brien's test demonstrated 90% sensitivity for arthroscopically-confirmed SLAP lesions 3, making it highly effective. However, its specificity for SLAP lesions is lower when AC joint pathology is present—it showed 95% specificity for AC joint lesions but only 41% sensitivity 2.
Critical Clinical Algorithm
When O'Brien's test is positive:
- Pain location at AC joint = AC pathology more likely
- Deep shoulder pain that improves with supination = SLAP lesion more likely
- Combining O'Brien's test with Mayo shear and Jobe's relocation tests achieves 100% sensitivity for SLAP lesions 3
Common Pitfall
MRI and MR arthrography have lower sensitivity (50-72%) than physical examination for SLAP lesions 3. Do not rely solely on imaging—the physical examination should remain central to diagnosis. When clinical suspicion is high despite negative imaging, consider arthroscopy based on examination findings alone.