When a person experiences shoulder pain, clinicians often use specific movement patterns called orthopedic special tests. These tests help isolate and assess structures within the shoulder joint, such as muscles, tendons, and cartilage. By observing a patient’s reaction—pain, weakness, or clicking—during these maneuvers, the clinician can narrow down the potential source of the problem. Two common tests used are the Empty Can Test and the O’Brien’s Test. While both evaluate shoulder integrity, they target fundamentally different anatomical structures, making the choice dependent on the suspected injury.
The Empty Can Test
The Empty Can Test, also known as Jobe’s Test, is primarily used to evaluate the health of the supraspinatus muscle and its tendon. The supraspinatus is one of the four rotator cuff muscles, playing a role in lifting the arm away from the body. This test is a crucial tool when a clinician suspects a rotator cuff tear, tendonitis, or a related condition like subacromial impingement.
The procedure involves the patient standing or sitting with their arm positioned at a 90-degree angle, lifted out to the side and slightly forward (the scapular plane). The arm is then rotated internally, turning the thumb downward, similar to the motion of emptying a beverage can. The clinician applies a downward force to the arm, and the patient is asked to resist this pressure.
A positive result is noted if the patient experiences pain or exhibits noticeable weakness against the resistance compared to the unaffected shoulder. Pain alone may suggest tendonitis or irritation of the tendon as it passes under the bony arch of the shoulder. Weakness, especially when severe, can strongly suggest a partial or full-thickness tear of the supraspinatus tendon.
The O’Brien’s Test
The O’Brien’s Test, also called the Active Compression Test, is designed to provoke symptoms related to the superior labrum and the acromioclavicular (AC) joint. The labrum is a ring of cartilage around the shoulder socket, and a tear in the upper portion is often referred to as a SLAP (Superior Labrum Anterior to Posterior) lesion. This test is frequently used for athletes, particularly those involved in repetitive overhead activities like throwing.
The test is performed in two distinct phases. In the first phase, the patient raises their arm forward to 90 degrees, brings it slightly across the body, and internally rotates the arm so the thumb points down. The clinician then applies a downward force that the patient resists. The test is repeated in the second phase, where the arm remains in the same position, but the patient externally rotates it so the palm faces up, and the thumb points upward.
For the test to be considered positive for a SLAP lesion, the patient must experience pain or a painful clicking sensation during the first phase (thumb down) that is lessened or completely relieved in the second phase (thumb up). If the pain is felt superficially at the top of the shoulder in both positions, it is more indicative of pathology within the AC joint, where the collarbone meets the shoulder blade.
Diagnostic Targets and Clinical Reliability
The primary difference between the two tests lies in the type of tissue they are designed to assess. The Empty Can Test targets contractile tissue, specifically the supraspinatus muscle and its tendon, which generate movement and force. Conversely, the O’Brien’s Test is primarily aimed at non-contractile, static stabilizing structures, namely the superior labrum cartilage and the ligaments and capsule of the AC joint. This distinction guides the clinician’s initial choice, as the patient’s history—such as a specific traumatic event versus chronic overhead use—will suggest one target over the other.
A clinician will opt for the Empty Can Test when the patient reports pain with lifting or raising the arm, or when there is suspicion of a rotator cuff tear or impingement syndrome. The O’Brien’s Test is preferred when the patient describes a deep, mechanical symptom like clicking, catching, or popping, often following an injury from a fall or sudden, forceful movement. While the Empty Can Test is a reasonable screen for rotator cuff issues, the O’Brien’s Test is often viewed as less specific because a positive result can point to either a labral tear or an AC joint problem.
The diagnostic value of both tests is measured by concepts like sensitivity and specificity, which describe how accurately a test detects or rules out a condition. Studies show that the reliability of these shoulder special tests can vary widely, and no single test is definitive on its own.
For instance, the O’Brien’s Test has demonstrated a broad range of sensitivity and specificity values across different studies for detecting SLAP lesions, sometimes showing high sensitivity but low specificity. The Empty Can Test has been found to have a relatively low sensitivity for supraspinatus tears, meaning it can miss a tear that is actually present. For this reason, clinicians rarely rely on a single positive test result, instead using a cluster of tests and often requiring confirmation through advanced imaging techniques, such as an MRI, to secure a final diagnosis and treatment plan.