The empty can test checks for damage to the supraspinatus, a small but critical muscle and tendon that sits on top of your shoulder and helps you lift your arm. First described by Jobe and Moynes in 1982, it’s one of the most commonly used physical examination tests for suspected rotator cuff tears. If you’ve had shoulder pain, weakness when raising your arm, or difficulty reaching overhead, there’s a good chance a doctor or physical therapist will put you through this test as a first step toward figuring out what’s going on.
What the Test Is Looking For
Your rotator cuff is a group of four muscles that stabilize the shoulder joint. The supraspinatus runs along the top of your shoulder blade and attaches to the top of your upper arm bone. It’s the rotator cuff muscle most vulnerable to tears, partly because of its position: it passes through a narrow space beneath a bony arch at the top of your shoulder, where it can get pinched or worn down over time.
The empty can test is designed to isolate the supraspinatus so your examiner can assess whether the tendon is intact, partially torn, or completely torn. It does this by placing your shoulder in a very specific position that forces the supraspinatus to do most of the work against resistance.
How the Test Is Performed
You’ll be asked to raise both arms out to the side to shoulder height (90 degrees of abduction). From there, you angle your arms forward about 30 degrees so they’re in what’s called the scapular plane, which is the natural angle of your shoulder blade. Then you rotate your arms inward so your thumbs point toward the floor, as if you were pouring out a can of soda. That’s where the name comes from.
With your arms in this thumbs-down position, the examiner pushes down on your forearms or wrists while you try to hold them in place. The test is done on both sides so the examiner can compare your injured shoulder to your healthy one.
What a Positive Result Means
There are two things the examiner is watching for: weakness and pain. Both count as positive findings, but they point to different things.
If you can’t resist the downward pressure and your arm drops or gives way, that signals muscle weakness. This could indicate a tear in the supraspinatus tendon. However, weakness alone isn’t specific enough to confirm a rotator cuff tear. Research published in The Open Orthopaedics Journal found that weakness during the empty can test has low specificity, meaning other conditions can produce the same result. One important example is cervical spondylotic amyotrophy, a condition where nerve compression in the neck causes shoulder muscle weakness that mimics a rotator cuff tear.
Pain during the test is actually a more telling sign. The same research found that pain provocation during the empty can test has high specificity and high predictive value for rotator cuff tears specifically. If the test hurts, a neck-related cause is much less likely. If you only show weakness without pain, your examiner should consider the possibility that the problem originates in your cervical spine rather than the shoulder itself.
Empty Can vs. Full Can Test
You may also be tested in what’s called the “full can” position. The setup is identical except your thumbs point up toward the ceiling instead of down toward the floor. This matters more than it sounds.
The thumbs-down empty can position can be painful even in people without shoulder problems because it compresses the supraspinatus tendon in the narrow subacromial space at the top of the shoulder. Several research groups have noted that this built-in impingement effect can trigger pain that has nothing to do with a tear, potentially muddying the results. It can also make it harder for you to fully engage the supraspinatus, since pain naturally inhibits muscle contraction.
Electromyographic studies, which measure how hard muscles are working, show that the supraspinatus contracts at similar levels in both the empty can and full can positions. But the full can position is less likely to cause impingement and is generally less painful. For this reason, many clinicians now consider the full can test a better option, especially if you already have signs of subacromial impingement. Some examiners will run both versions to get a fuller picture.
Limitations of the Test
The empty can test is a screening tool, not a definitive diagnosis. It’s useful for raising suspicion of a supraspinatus problem, but it has real limitations. The thumbs-down position doesn’t isolate the supraspinatus as cleanly as once thought. Research using electromyography has shown that the classic empty can position produces a relatively low ratio of supraspinatus activity compared to surrounding shoulder muscles, meaning other muscles like the deltoid are doing a significant share of the work. This makes it harder to pinpoint the supraspinatus as the sole source of weakness.
False positives can also come from subacromial bursitis (inflammation of the cushioning tissue in the shoulder), general shoulder impingement, and the cervical spine issues mentioned earlier. A single positive empty can test, taken in isolation, isn’t enough to confirm a rotator cuff tear.
What Happens After a Positive Test
If the empty can test is positive, especially for both pain and weakness, your provider will typically order imaging to get a direct look at the tendon. Ultrasound and MRI are the two most common options. Ultrasound is quick and can show tears in real time as you move your shoulder. MRI provides a more detailed view of the soft tissue and can distinguish between partial and full-thickness tears, which matters for treatment planning.
In most cases, the empty can test is one of several physical exam maneuvers performed together. Your examiner will likely combine it with tests targeting the other rotator cuff muscles and the shoulder labrum to build a more complete clinical picture before deciding on next steps.