O’Brien’s Test, also known as the Active Compression Test, is a physical examination maneuver used by healthcare professionals. This diagnostic tool helps assess shoulder pain and identify potential underlying pathologies. It involves a series of arm movements and resistance to pinpoint the source of discomfort within the shoulder joint.
Conditions It Identifies
The O’Brien’s Test identifies a Superior Labrum Anterior Posterior (SLAP) lesion. A SLAP lesion is a tear in the glenoid labrum, a ring of cartilage surrounding the shoulder socket where the biceps tendon attaches. These tears can extend from the front to the back of this attachment point and may involve the biceps tendon itself. SLAP lesions are common in overhead throwing athletes due to repetitive stress, or they can result from acute trauma like falling onto an outstretched arm.
The test also identifies pathology of the acromioclavicular (AC) joint. The AC joint connects the clavicle (collarbone) to the acromion, a part of the shoulder blade. AC joint pathology can involve degeneration, such as osteoarthritis, or instability from trauma like a direct blow to the shoulder or a fall. These conditions can cause pain on top of the shoulder, tenderness, and difficulty with certain arm movements.
Performing and Interpreting the Test
A clinician performs the O’Brien’s Test by having the patient stand with their arm flexed forward to 90 degrees, elbow extended, and horizontally adducted about 10 degrees across the body. The patient then internally rotates their arm, pointing the thumb downward. In this position, the clinician applies a downward force to the patient’s arm, and the patient resists.
The test is repeated with the patient’s arm in maximum external rotation (thumb pointing upward), again resisting a downward force. A “positive” O’Brien’s Test occurs if pain is experienced during the internally rotated position and this pain significantly reduces or disappears during the externally rotated position. If pain or clicking is felt deep inside the shoulder during the internally rotated phase, it may indicate a SLAP lesion. Conversely, pain felt at the top of the shoulder, over the AC joint, suggests AC joint pathology.
Why This Test Matters
The O’Brien’s Test is a valuable component of a comprehensive physical examination for shoulder pain. While it can help direct a clinician toward a potential diagnosis, it is not a standalone diagnostic tool. Its findings are often correlated with other physical tests and imaging studies, such as an MRI, to reach a definitive diagnosis. This approach ensures accurate identification, guiding treatment plans or further investigation for persistent shoulder discomfort.