O'Brien's Test and Crank Test: Superior Labrum (SLAP Tear) Assessment Guide
In short
Superior Labrum Anterior to Posterior (SLAP) tears challenge shoulder diagnostics. Learn how O'Brien active compression test and the Crank test differentiate labral tears from acromioclavicular joint pathology.
In this guide (5 sections)
Anatomy of SLAP Tears and O'Brien's Rationale
The superior glenoid labrum anchors the long head of the biceps tendon to the glenoid rim. In overhead throwing athletes, cricket fast bowlers, or following a fall onto an outstretched hand, repetitive traction or torsional peel-back causes SLAP tears.
The Active Compression Test of O'Brien places the long head of the biceps under maximum tension while compressing it against the superior glenoid rim.
How to Perform O'Brien's Active Compression Test
O'Brien's test is a two-part comparative maneuver performed in standing or sitting:
- Position 1 (Pronated & Adducted): The patient elevates the affected arm to 90 degrees of forward flexion, horizontally adducts 10 to 15 degrees across midline, and fully internally rotates the arm so the thumb points toward the floor. The clinician applies a downward force to the wrist while the patient resists.
- Position 2 (Supinated & Adducted): The patient rotates their arm into full supination so the palm faces upward, maintaining the same elevation and adduction angle. The downward force is repeated.
- Interpretation for SLAP Tear: Pain or painful clicking located deep inside the glenohumeral joint in Position 1 that is relieved or abolished in Position 2 confirms a positive SLAP tear.
- Interpretation for AC Joint Pathology: If the pain is felt superficially on top of the shoulder directly over the acromioclavicular joint in both positions, it indicates AC joint arthropathy rather than a deep labral tear.
The Crank Test for Labral Shearing
The Crank test shears the labrum between the humerus and glenoid cavity. With the patient upright or supine, the arm is elevated to 160 degrees in the scapular plane with elbow flexed to 90 degrees. The clinician applies gentle axial compression along the humerus while rotating the arm internally and externally. A positive finding is a click or reproduction of deep catching pain.
Diagnostic Accuracy Comparison
| Test Name | Sensitivity | Specificity | Key Differential | |
|---|---|---|---|---|
| O'Brien Active Compression | 67 to 88 percent | 49 to 73 percent | Distinguishes deep labral pain from superficial AC joint pain | |
| Crank Test | 46 to 77 percent | 56 to 83 percent | Detects mechanical labral flap entrapment during rotation | |
| Biceps Load Test II | 89 percent | 96 percent | Highly accurate in overhead athletes at 120° abduction |
Frequently Asked Questions
Can a SLAP tear heal with conservative physiotherapy?
Type I (fraying) and many Type II SLAP tears respond well to conservative physiotherapy focusing on restoring posterior capsule mobility (sleeper stretch), rotator cuff dynamic balance, and scapular dyskinesis correction before considering surgery.
Why does supinating the hand relieve pain in a SLAP tear?
Supination rotates the greater tuberosity away from the superior glenoid rim and reduces torsional peel-back tension on the long head of the biceps anchor.
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