The O’Brien’s Test, also known as the Active Compression Test, is a common physical examination technique used by orthopedic specialists and physical therapists when a shoulder injury is suspected. This test is a “provocative” maneuver designed to intentionally reproduce a patient’s pain or symptoms by stressing specific structures within the shoulder joint. Performing the test in two distinct phases helps the clinician narrow down the potential cause of discomfort. The results guide further diagnostic steps necessary for an accurate diagnosis and treatment plan.
The Purpose and Procedure of the O’Brien’s Test
The O’Brien’s Test procedure involves two distinct phases. Both phases are performed with the patient’s arm positioned at 90 degrees of forward flexion and slightly across the body (10 to 15 degrees of horizontal adduction). The initial phase requires the patient’s arm to be internally rotated, with the thumb pointing downward. The examiner then applies a downward force to the forearm while the patient resists this pressure.
The thumb-down position in the first phase is thought to stress the superior aspect of the labrum and the biceps tendon anchor. This orientation places a compressive and shearing load on the internal structures of the shoulder joint. The second phase involves the patient externally rotating their arm so the palm faces upward.
The examiner repeats the downward resistance against the patient’s forearm in this second position. Comparing the two phases is essential to observe a change in symptoms, which defines a positive result. If the patient experiences pain or a painful clicking sensation during the first phase, but that pain is significantly reduced or eliminated in the second phase, the test provides a meaningful clinical sign.
Interpreting a Positive Result
A positive O’Brien’s Test is defined by a specific pattern of symptoms. Pain or a painful click occurs during the first phase (thumb down/internal rotation) and is relieved or significantly lessened during the second phase (palm up/external rotation). This differential response between the two positions, not just the presence of pain in one position, serves as the diagnostic indicator. The thumb-down position introduces a “peel-back” force on the superior labrum, which is relieved upon external rotation.
Understanding the location of the pain is important when interpreting a positive result. If the pain is felt deep inside the glenohumeral joint, it points toward a problem with the cartilage rim, or labrum. Conversely, if the pain is localized to the top of the shoulder, directly over the acromioclavicular (AC) joint, it suggests a pathology in that joint instead. A noticeable clicking or popping sensation accompanying the pain in the first position further suggests a mechanical issue with the labrum.
Diagnoses Associated with a Positive Test
The primary condition suggested by a positive O’Brien’s Test is a Superior Labrum Anterior to Posterior (SLAP) lesion. This is a tear in the upper portion of the labrum where the long head of the biceps tendon attaches. This injury is common in athletes who perform repetitive overhead motions, such as throwing or serving a tennis ball. The specific arm position in the first phase stresses the biceps-labral complex, reproducing the pain associated with the tear.
A positive result can also be associated with problems in the acromioclavicular (AC) joint, the junction between the collarbone and the shoulder blade. If the patient reports pain concentrated directly at the top of the shoulder during the first phase, it suggests AC joint pathology, such as arthritis or a separation. In this case, the pain is caused by the compressive force on the AC joint, not the stress on the labrum. Recent research suggests the test may be more sensitive for certain posteroinferior labral tears than for SLAP lesions, despite its original design.
Limitations and Follow-Up Steps
Despite its usefulness as a screening tool, the O’Brien’s Test is not a definitive diagnostic measure and has limitations. No single physical exam maneuver can provide a complete diagnosis for complex shoulder injuries. The test has a moderate level of specificity, meaning it can sometimes produce a false-positive result in patients with other shoulder conditions, such as rotator cuff tendinopathy.
A positive test result directs the physician toward a likely diagnosis, but confirmation through advanced imaging is necessary. The most common next step is a Magnetic Resonance Imaging (MRI) scan, often performed with a contrast dye injected into the joint (MR arthrogram), to better visualize soft tissues like the labrum. Once the diagnosis is confirmed, a treatment pathway is established, which may involve physical therapy for rehabilitation or, for severe tears, a surgical consultation to repair the damaged structure.