The Jobe’s Empty Can Test, also known as the Supraspinatus Test, is a standardized physical examination maneuver used by healthcare professionals to evaluate the health of the shoulder joint. This maneuver helps identify potential injury, inflammation, or dysfunction within the rotator cuff. The primary purpose of the test is to assess the integrity of the structures responsible for lifting the arm away from the body against resistance. It is a diagnostic tool performed in an office setting to narrow down the possible causes of a patient’s shoulder pain or weakness before considering advanced imaging.
The Supraspinatus Muscle
The Supraspinatus muscle is the smallest of the four muscles that make up the rotator cuff group, which collectively provide dynamic stability to the shoulder joint. This muscle is located in a depression on the back of the shoulder blade known as the supraspinous fossa, running beneath a bony projection called the acromion. Its tendon attaches to the superior facet of the greater tubercle of the humerus.
The main function of the supraspinatus is to initiate arm abduction, the movement of lifting the arm out to the side. It is most active during the first 0 to 15 degrees of this motion before the larger deltoid muscle takes over the majority of the work. The muscle also stabilizes the joint by keeping the head of the humerus pressed into the glenoid cavity. Due to its location and its passage through the small space beneath the acromion, the supraspinatus tendon is frequently subjected to compression and friction, making it one of the most commonly damaged components of the rotator cuff.
Executing the Examination
To perform the Jobe’s Empty Can Test, the patient is typically seated or standing upright. The patient is asked to abduct the arm to approximately 90 degrees.
The arm is then moved forward about 30 degrees, placing it in the scapular plane, a more natural angle for the joint. The test gets its name from the next step, where the patient fully internally rotates the arm so the thumb points toward the floor, mimicking emptying a beverage can. This rotation further compresses the supraspinatus tendon under the acromion.
Once the arm is in the correct position, the examiner applies a steady downward pressure against the patient’s forearm or wrist. The patient is instructed to actively resist this downward force and try to hold the arm steady in the elevated position. The clinician performs the test on both shoulders to compare the strength and response of the affected arm against the unaffected side.
Interpreting Pain and Weakness
Interpretation of the Jobe’s test relies on observing two outcomes: pain provocation or weakness demonstration. A positive test result is indicated if the patient experiences either pain, weakness, or both, when attempting to resist the examiner’s downward pressure. The presence of pain alone during the test often suggests irritation, inflammation, or tendinopathy of the supraspinatus tendon.
Significant weakness or an inability to resist the downward force, especially compared to the opposite arm, suggests a structural compromise. This weakness may point toward a partial or full-thickness tear within the supraspinatus muscle or its tendon. Weakness can also indicate a problem with the nerve supply to the muscle, known as suprascapular nerve neuropathy, which affects muscle control.
A result showing both pain and weakness increases the likelihood of a significant pathology affecting the rotator cuff. While the Empty Can Test is a valuable tool for directing a diagnosis, it is rarely definitive on its own. Clinicians use the results alongside the patient’s medical history and other physical tests. Confirmation often requires imaging techniques, such as magnetic resonance imaging (MRI), to establish an accurate final diagnosis.