What Does a Positive Empty Can Test Indicate?

A positive empty can test points toward a problem with the supraspinatus, the rotator cuff muscle that runs along the top of the shoulder blade and helps lift the arm. The test was originally designed to confirm a supraspinatus tendon tear, and a positive result traditionally means the patient felt pain or could not resist the examiner’s downward force during the maneuver. But the picture is more nuanced than a single pass-or-fail result, and how the test comes back positive matters as much as whether it does.

How the Test Is Performed

The empty can test, also called the Jobe test after the orthopedic surgeon who first described it, places the shoulder in a very specific position. You stand with your arm raised to about 90 degrees out in front of you, angled roughly 30 to 45 degrees toward the midline of your body so it sits in the plane of the shoulder blade. Then you rotate your arm inward so that your thumb points toward the floor, as though you were pouring out a can of soda. The examiner pushes down on your forearm or wrist while you try to hold your arm in place.

The idea behind the position is that it isolates the supraspinatus as much as possible. With the arm in that thumbs-down orientation, several other muscles around the shoulder are placed at a mechanical disadvantage, which in theory forces the supraspinatus to do most of the work holding the arm up against the examiner’s push. The shoulder’s positioning also activates the middle deltoid and the subscapularis to maintain abduction, while limiting the contribution of the other rotator cuff muscles.

Pain Versus Weakness

There are two distinct ways the empty can test can come back positive, and the distinction changes what the result means. One is pain: you can hold your arm up against the push, but it hurts to do so. The other is weakness: you physically cannot resist the downward force, and your arm drops. A third possibility is both at once.

Traditionally, pain during the test suggests supraspinatus tendon pathology, which could range from tendinitis and partial tears to impingement of the tendon beneath the acromion. Weakness, on the other hand, is more suggestive of a significant tear in the supraspinatus tendon, because a torn tendon simply cannot generate the force needed to hold the arm in position. One study comparing the empty can and full can tests found that interpreting weakness as the criterion for a torn supraspinatus yielded about 70% accuracy for the empty can test.

But pain alone is not as straightforward to interpret. Research on subacromial lidocaine injections has shown that when you numb the space above the rotator cuff before repeating the test, many previously positive results become negative. That finding suggests a meaningful share of positive empty can tests are driven by pain from bursal inflammation rather than by structural damage to the tendon itself. In other words, an inflamed bursa can mimic the appearance of a torn or diseased supraspinatus on clinical examination.

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What the Numbers Say About Accuracy

The empty can test is reasonably sensitive, meaning it does a decent job catching people who truly have a supraspinatus problem. In a large cohort study, the test’s sensitivity for supraspinatus tears was about 88%, with a specificity of roughly 62%.

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That combination tells you something important about what a positive test can and cannot do. High sensitivity with moderate specificity means the test is better at ruling a problem out than ruling it in. If the test is negative, there is a reasonably good chance your supraspinatus is intact. But if the test is positive, there is still a fair probability the result is a false alarm, driven by something other than a supraspinatus tear.

A systematic review looking specifically at subacromial impingement syndrome reached a similar conclusion. The empty can test, along with the Hawkins-Kennedy test and Neer’s sign, showed pooled sensitivity in the range of 69% to 78% and specificity between 57% and 62%, making these tests more useful for ruling out impingement than confirming it.

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That said, for confirming subacromial impingement specifically, the empty can test does carry a positive likelihood ratio that pushes past the useful threshold. One study found a positive likelihood ratio of about 3.9 for the empty can test in subacromial impingement, meaning a positive result nearly quadruples the pre-test odds that impingement is present. Combined with a painful arc and external rotation resistance test, the diagnostic picture gets more reliable.

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The Muscle Isolation Problem

The empty can test was designed under the assumption that the thumbs-down position forces the supraspinatus to work in relative isolation. Research over the past two decades has challenged that assumption fairly directly. An electromyography study recording from 13 shoulder muscles found that during the empty can position, eight or nine other shoulder muscles were activated to a similar degree as the supraspinatus. The researchers concluded that the test does not primarily activate the supraspinatus with minimal involvement from other muscles, and therefore does not satisfy a basic criterion for being a valid diagnostic tool for supraspinatus pathology alone.

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A PET/CT study looking at metabolic muscle activity confirmed a related finding. In the empty can position, the middle deltoid showed the most significant increase in activity, and its activity was significantly greater than the supraspinatus. The supraspinatus, middle deltoid, and subscapularis all showed more activity in the empty can position compared with the full can position, but the deltoid dominated.

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Separate EMG work found that middle deltoid activity during the empty can exercise averaged about 77% of maximum voluntary contraction, which was significantly higher than during the full can exercise. Supraspinatus activity, meanwhile, did not differ statistically across the empty can, full can, and prone full can exercises.

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This does not mean the empty can test is useless. It means the test is not a clean window into the supraspinatus alone. Pain or weakness during the maneuver could reflect problems with other shoulder structures, including the deltoid or subscapularis, and clinicians are increasingly interpreting positive results as a general indicator of shoulder pathology rather than supraspinatus-specific pathology.

Empty Can Versus Full Can

The full can test was introduced as a less provocative alternative. The arm position is nearly identical, except your thumb points upward instead of down, as though you were holding a full can you did not want to spill. This puts the shoulder in a slightly externally rotated position rather than the internally rotated one used in the empty can test.

In terms of diagnostic accuracy for detecting a torn supraspinatus, the two tests perform similarly. The study that compared them head-to-head found about 75% accuracy for the full can test and 70% for the empty can test when weakness was the criterion, and the difference was not statistically significant.

The practical difference between the two lies in comfort and shoulder mechanics. The empty can position produces greater scapular upward rotation, more clavicular elevation, and less posterior tilt of the scapula compared with the full can position, but the space between the acromion and the humeral head, which is the tight corridor where impingement occurs, does not actually differ between the two positions.

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The empty can position tends to provoke more pain in patients with shoulder problems, likely because the internal rotation component compresses already irritated structures. For patients who find the empty can position too painful to perform reliably, the full can test can provide comparable diagnostic information without as much discomfort. Many clinicians now perform both and compare the results.

Conditions a Positive Test Can Point To

A positive empty can test does not diagnose one specific condition. Depending on whether the finding is pain, weakness, or both, and depending on what other tests come back positive, the differential includes several shoulder problems.

Supraspinatus tear: Weakness that causes the arm to drop or collapse under the examiner’s pressure is the classic indicator. Full-thickness tears tend to produce obvious weakness, while partial tears may produce a combination of pain and mild weakness.
Subacromial impingement: Pain without frank weakness is more common in impingement syndrome, where the supraspinatus tendon gets pinched beneath the acromion during overhead movements. The empty can test is one of several clinical tests used together to build a case for this diagnosis.
Supraspinatus tendinitis or tendinopathy: An inflamed or degenerating tendon that is not yet torn can still produce significant pain during the test, especially under load.
Subacromial bursitis: As the lidocaine injection research showed, inflammation of the bursa sitting above the rotator cuff can cause a positive result that looks identical to tendon pathology on clinical examination.

One complication worth knowing about is that weakness during the empty can test can also come from nerve problems unrelated to the rotator cuff. A study examining patients with cervical spondylotic amyotrophy, a condition where nerve compression in the neck causes muscle wasting in the shoulder, found that muscle weakness on the empty can test could not differentiate between a rotator cuff tear and nerve-related muscle loss. Pain provocation during the test was a more useful distinguishing feature.

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Examiner Agreement Is Only Fair

Another practical limitation of the empty can test is how consistently different clinicians interpret it. A pilot study comparing an experienced and a novice clinician found only fair agreement on the empty can test, with a kappa statistic of 0.297. By comparison, the Hawkins-Kennedy test achieved perfect agreement between the two examiners. The painful arc test landed at moderate agreement.

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A kappa of 0.297 means two clinicians looking at the same patient may disagree on whether the test is positive more often than you might expect. Part of the problem is the judgment call involved in interpreting subtle weakness versus guarded movement due to pain, versus a patient who simply does not understand the instructions. A test that relies heavily on the examiner’s subjective feel of how much resistance the patient is generating will naturally vary between practitioners. This is one reason the empty can test is almost never used in isolation to make a clinical decision.

Why Clinicians Combine Multiple Tests

Given the empty can test’s moderate specificity, its imperfect ability to isolate the supraspinatus, and the variability between examiners, no experienced clinician will diagnose a rotator cuff tear based on a single positive empty can test. The test is most informative when combined with other shoulder examination maneuvers. A painful arc test, an external rotation resistance test, and the Hawkins-Kennedy test each probe the shoulder from different angles and stress different structures. When several of these tests all come back positive, the cumulative evidence for a rotator cuff or impingement problem becomes much stronger than any single test alone.

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Imaging typically follows when the clinical picture warrants it. An MRI can show the exact location and size of a tear, the degree of tendon retraction, and whether there is muscle atrophy, all of which affect treatment decisions in ways that a physical exam alone cannot determine. Ultrasound is another option that is faster and cheaper, though it depends more heavily on the operator’s skill. The physical exam, including the empty can test, serves as the gateway to those imaging decisions rather than the endpoint.

Tracking Strength After Rotator Cuff Surgery

Beyond its diagnostic role, the empty can test also serves as a measurement tool for tracking shoulder recovery. In rotator cuff repair research, clinicians use a handheld force gauge to quantify how much downward pressure a patient can resist in the empty can and full can positions before and after surgery. A prospective randomized trial of rotator cuff repair found that after surgery, patients improved their empty can strength by about 54% and their full can strength by about 66%, with similar gains regardless of whether a single-row or double-row surgical technique was used.

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In this context, the test stops being a yes-or-no diagnostic maneuver and becomes a quantitative strength benchmark. A patient who could resist only a few pounds of force before surgery and who now resists substantially more has concrete evidence that the repair is healing and the supraspinatus is regaining function. Many physical therapy programs use periodic empty can and full can strength measurements to guide progression through rehabilitation stages, decide when to introduce overhead activities, and determine when an athlete is ready to return to sport.