O’Brien’s test is a physical exam maneuver used to check for two common sources of shoulder pain: tears in the labrum (the ring of cartilage that lines the shoulder socket) and problems with the acromioclavicular (AC) joint, the small joint where your collarbone meets the top of your shoulder blade. Also called the active compression test, it was developed by orthopedic surgeon Dr. Stephen J. O’Brien as a quick, in-office way to pinpoint these injuries without imaging.
What the Test Is Looking For
The test primarily targets SLAP lesions, which are tears in the upper portion of the labrum. “SLAP” stands for superior labrum anterior to posterior, describing where the tear runs along the top of the cartilage ring. These injuries are common in overhead athletes like baseball players, swimmers, and tennis players, but they also happen from falls, car accidents, or repetitive lifting. The labrum helps keep the ball of the upper arm bone seated in the shallow shoulder socket, so when it tears, you can get deep pain, catching sensations, or a feeling of instability.
O’Brien’s test also helps identify AC joint problems. Because the two conditions cause pain in different locations during the same maneuver, the test can help distinguish between them in a single exam.
How the Test Is Performed
The test has two phases, and the comparison between them is what makes it useful. You’ll be standing or sitting, and the examiner will guide you through both positions.
In the first phase, you raise your arm straight out in front of you to 90 degrees (shoulder height) with your elbow fully extended. Your arm is then brought about 10 to 30 degrees across your body toward the midline. From this position, you rotate your arm so your thumb points down toward the floor (internal rotation). The examiner places a hand on your wrist and asks you to push your arm upward against their resistance.
In the second phase, everything stays the same except you rotate your arm so your palm faces the ceiling (external rotation, thumb pointing up). The examiner again resists as you push upward. The key is whether your pain changes between the two positions.
Why the Two Positions Matter
Switching between internal and external rotation changes how the upper arm bone sits against the shoulder socket. When your thumb points down, the arm bone rotates inward and compresses the labrum and the AC joint. This is the “loaded” position. When your thumb points up, the arm bone rotates outward and takes pressure off those structures.
If pain is present during the thumb-down phase and significantly improves or disappears during the thumb-up phase, the test is considered positive. The location of the pain during the thumb-down phase helps narrow down the cause. Deep pain felt inside the shoulder joint suggests a labral tear, while pain localized to the top of the shoulder, right where the collarbone meets the shoulder blade, points toward an AC joint problem.
How Reliable Is the Test
O’Brien’s test is one of the most widely used physical exams for labral tears, but no single shoulder test is definitive on its own. The test was originally described specifically for diagnosing SLAP lesions, and it remains a standard part of the shoulder exam for that purpose. Interestingly, more recent research published in the Journal of Shoulder and Elbow Surgery found that the test may actually be better at identifying tears in the lower and back portions of the labrum (posteroinferior tears) than it is at catching the superior tears it was originally designed to detect.
Because of this variability, clinicians typically combine O’Brien’s test with other physical exam maneuvers and, when needed, imaging like an MRI or MRI with contrast dye injected into the joint (an MR arthrogram) to confirm a diagnosis. A positive O’Brien’s test raises suspicion, but it’s one piece of a larger diagnostic picture.
What a Positive Result Means for You
If your examiner gets a positive O’Brien’s test, it doesn’t automatically mean you need surgery. It means there’s likely something going on with the labrum or the AC joint that warrants further evaluation. Many labral tears, particularly smaller or less symptomatic ones, respond well to physical therapy focused on strengthening the rotator cuff and the muscles that stabilize the shoulder blade. AC joint issues similarly often improve with rest, activity modification, and targeted rehab.
If your symptoms are severe, if you have mechanical symptoms like clicking or locking, or if conservative treatment doesn’t help after several weeks, imaging and potentially a referral to an orthopedic specialist are typical next steps. For athletes whose sport involves overhead motions, the threshold for further workup tends to be lower because labral tears in that population are less likely to resolve without more targeted intervention.
What to Expect During the Exam
The test itself takes less than a minute. It can reproduce your pain briefly, but it shouldn’t cause any lasting discomfort. Your examiner will likely perform several other shoulder tests in the same visit, checking the rotator cuff, testing for impingement, and assessing range of motion. O’Brien’s test works best as part of this broader exam rather than in isolation, so don’t be surprised if your provider runs through a series of maneuvers before discussing what they think is going on.