O’Brien’s Test, also known as the Active Compression Test, is a common technique utilized during the physical examination of a patient presenting with shoulder pain. Clinicians, such as physicians and physical therapists, employ this maneuver to help identify the potential source of a patient’s symptoms. It is a two-part procedure that involves specific movements and resistance designed to provoke pain or other sensations within the shoulder complex. By comparing the patient’s reaction across the two distinct phases, the examiner can gather information to narrow down the possible causes of the shoulder discomfort.
What the Test Screens For
The primary purpose of the O’Brien’s Test is to evaluate the integrity of the superior aspect of the glenoid labrum, which is a ring of cartilage that lines the shoulder socket. It is designed to stress the area where the long head of the biceps tendon attaches to the labrum. This region is susceptible to a Superior Labral Anterior Posterior (SLAP) lesion, a tear in the upper rim of the shoulder socket cartilage. The test is also effective at screening for issues localized to the acromioclavicular (AC) joint, where the collarbone meets the shoulder blade. The specific arm positioning creates a compressive force that stresses both the superior labrum and the AC joint simultaneously. This dual function allows the test to differentiate between two distinct anatomical sources of pain.
How the Test is Performed
The O’Brien’s Test is performed with the patient typically standing or sitting, and it involves two sequential phases of resistance. The clinician instructs the patient to raise their arm to 90 degrees of forward flexion, bringing the arm slightly across the body into approximately 10 to 15 degrees of horizontal adduction. Keeping the elbow extended, the patient then internally rotates their arm so the thumb points downward, a position known as pronation.
Phase 1 (Internal Rotation/Pronation)
In the first phase, the examiner applies a steady downward force to the patient’s forearm, while the patient is instructed to resist this pressure. This action maximally loads and compresses both the AC joint and the superior labrum. If pain is reported during this resisted movement, the examiner notes the location of the discomfort, whether it is deep within the joint or superficial at the top of the shoulder. This initial phase is designed to provoke symptoms related to the suspected injury. The specific position of internal rotation and horizontal adduction mechanically displaces the biceps tendon, placing tension on the bicipital-labral complex. The thumb-down position is the provocative maneuver necessary to elicit pain or a painful clicking sensation.
Phase 2 (External Rotation/Supination)
Immediately following the first phase, the arm position is altered while maintaining 90 degrees of flexion and 10 to 15 degrees of adduction. The patient externally rotates their arm so the palm faces upward, or the thumb points upward (supination). The clinician repeats the downward pressure on the forearm, and the patient is again asked to resist the force. This change in rotation is designed to alter the mechanical stress on the structures within the shoulder joint. The comparison of the patient’s symptoms between the two phases is the most important element of the test.
Interpreting the Results
Interpretation of the O’Brien’s Test relies on comparing the patient’s symptoms between the two phases. A positive result is not simply the presence of pain, but a specific change in pain or sensation between the two maneuvers.
Positive for SLAP Lesion
A test is positive for a SLAP lesion if the patient reports pain or a painful clicking sensation deep within the shoulder during Phase 1 (thumb down), which is significantly reduced or eliminated in Phase 2 (thumb up). The reduction in symptoms suggests that the change in rotation mechanically stabilizes the area, relieving the stress on the torn labrum. This difference in pain is the defining characteristic of a positive result for a superior labral tear.
Positive for AC Joint Pathology
The test may also indicate an issue with the acromioclavicular (AC) joint, but the finding is interpreted differently. If the patient reports pain localized over the AC joint during Phase 1, and this pain does not decrease or change notably in Phase 2, it suggests AC joint pathology. Compression of the joint is likely the source of the pain in both positions, rather than the mechanical shift of the labrum. O’Brien’s Test is one tool within a comprehensive physical examination. No single physical test is definitive; findings must be correlated with the patient’s medical history, other physical exam results, and often confirmed with advanced imaging, such as MRI.