AC resisted extension test

Key Takeaways

The AC resisted extension test provokes the acromioclavicular joint to localize shoulder pain.

A positive test reproduces sharp, well-localized pain on top of the shoulder at the AC joint.

Published research (Chronopoulos et al.) reports 72% sensitivity and 85% specificity, so the test earns its value inside an AC joint provocation cluster rather than on its own.

The free template records positioning, the resisted-abduction finding, the cluster result, and pain scores in one place, so every AC joint assessment is charted the same way.

Most guides to the AC resisted extension test stop at the single maneuver. But a positive result only becomes a confident call when you read it alongside the rest of the acromioclavicular joint provocation cluster and record the whole set the same way every time.

This guide is built for physical therapy practices and covers the correct technique, how to interpret a positive finding, the published diagnostic accuracy, and the sibling tests you should run with it, using the downloadable template above.

What is the AC resisted extension test?

The AC resisted extension test is a clinical assessment used to evaluate acromioclavicular (AC) joint dysfunction and injury. The AC joint is the articulation between the distal clavicle and the acromion of the scapula, at the very top of the shoulder.

It is a common source of pain in athletes, in people with repetitive overhead loads, and after a direct fall onto the shoulder. This special test applies resistance in a set position to provoke a symptomatic AC joint.

With the shoulder held at 90 degrees of flexion and internal rotation, the patient pushes the arm outward against the examiner’s hand. Pain localized to the AC joint during that resisted movement is a positive finding, pointing to AC joint pathology such as osteoarthritis, an AC joint separation, or a sprain — the sibling tests below help confirm which.

Structured documentation of the finding supports consistent, reproducible assessment across multiple visits.

How to perform the AC resisted extension test

Correct technique is what separates a true AC joint finding from a false positive, especially in sports medicine settings where overhead athletes are common. Follow these steps to perform the AC resisted extension test reliably:

1. Position the patient: Seat the patient with the arm relaxed. Bring the shoulder into 90 degrees of flexion (arm forward) with internal rotation, and flex the elbow to 90 degrees. This is the position that isolates the AC joint.
2. Take your stance: Stand behind or beside the patient. Place one hand on the outer side of the elbow to provide resistance. Rest your other hand lightly over the AC joint so you can feel for pain and crepitus as the patient moves.
3. Apply resistance: Ask the patient to push the elbow outward, into horizontal abduction, against your steady isometric resistance. Keep the force controlled rather than sudden.
4. Read the response: Ask the patient to point to where it hurts, and confirm the pain sits over the AC joint line, not the lateral deltoid or the rotator cuff. Ask directly whether it reproduces their familiar shoulder pain.
5. Record the finding: Note whether familiar pain is reproduced, its exact location, intensity on a 0-10 scale, and any weakness or apprehension. Use the downloadable template so the finding is captured the same way at every visit.

The two things that decide accuracy are the starting position and the direction of resistance. Resisting into horizontal abduction with the shoulder internally rotated loads the AC joint; letting the shoulder drift into pure adduction turns it into a different test. Pairing the maneuver with standardized note-taking keeps it reproducible from one session to the next.

Interpreting a positive AC resisted extension test

A positive AC resisted extension test reproduces pain localized specifically to the AC joint during resisted horizontal abduction. The pain should be sharp and well-localized, not diffuse shoulder ache.

Supporting positive findings include:

• Pain reproduced at 3-5/10 intensity or greater
• Pain over the palpable AC joint line, not the lateral shoulder or rotator cuff
• Weakness through the resisted movement, hinting at AC joint capsular involvement
• Recognition of familiar pain (for example, “that’s exactly where it hurts”)

A positive test points to AC joint pathology, typically osteoarthritis, post-separation change, or an acute AC joint sprain. It should never stand alone. Clinical assessment combines this test with palpation, the sibling AC joint special tests below, and imaging when indicated. Its diagnostic value climbs sharply when it is read as one result inside an AC joint test cluster.

Diagnostic accuracy: Sensitivity and specificity

The most commonly cited sensitivity and specificity figures for the AC resisted extension test come from Chronopoulos et al. (2004), who assessed physical tests for isolated chronic acromioclavicular lesions. The likelihood ratios below are commonly cited alongside these figures. These numbers guide how much weight to give a positive or negative result:

These figures show good specificity with moderate sensitivity. A positive test is fairly convincing for AC joint involvement, while a negative test lowers the odds without clearing the joint outright. The test performs best alongside clinical examination, patient history, a quality of life assessment, and imaging, never as a standalone diagnosis.

Related AC joint special tests

No single AC joint special test is accurate enough to diagnose on its own, which is why clinicians run them as a cluster. Combining two or three provocation tests, plus palpation for AC joint line tenderness, raises diagnostic confidence more than any one result.

Published clusters (such as those described by Krill and by Chronopoulos) pair the resisted extension test with the tests below. Here is how each one loads the joint differently:

Cross-body adduction test (scarf test)

With the patient seated, passively bring the arm across the body into horizontal adduction while supporting the elbow, so the shoulder folds toward the opposite side like a scarf. Pain at the AC joint is a positive sign.

Sometimes listed as the AC crossover test, the cross-body adduction test compresses the joint, so it complements the resisted extension test, which loads it in tension. This test is easy to document alongside the others.

Paxinos sign

The Paxinos sign is a manual AC compression test. Place your thumb under the posterolateral acromion and the index and middle fingers of the same hand on the mid-clavicle, then squeeze by pushing the thumb up and the fingers down.

Pain at the AC joint is a positive Paxinos test, which makes it a useful pressure-based counterpart to the resisted extension test.

AC shear test

Cup your interlocked hands over the shoulder, one heel on the spine of the scapula and the other on the clavicle, then squeeze your hands together to shear the AC joint. Pain or abnormal movement is a positive AC shear test, pointing to AC joint laxity or arthritis.

Because it stresses the joint through compression and shear rather than resisted motion, it adds a distinct data point to the cluster.

Active compression test (O’Brien’s test)

Position the shoulder at 90 degrees of flexion with about 10 to 15 degrees of horizontal adduction and full internal rotation, so the thumb points down. Ask the patient to resist a downward force, then repeat with the palm up.

In the active compression test, pain or clicking felt on top of the shoulder that eases when the palm is supinated suggests AC joint involvement (deeper pain can indicate a labral problem instead). It is the highest-volume search of the sibling tests, so patients and students often look it up by name.

A couple of others round out the picture. An AC traction test (also called the horizontal arm traction test) applies downward pull to the hanging arm and looks for a visible step or reproduced pain, which points to instability rather than arthritis.

AC joint line tenderness on palpation is the simplest screen of all and should anchor the cluster. Recording which tests you ran, and their results, is what turns a handful of maneuvers into a defensible AC joint test cluster.

How to document AC resisted extension test findings

Systematic documentation, similar to a structured neurological exam checklist, improves consistency and supports outcome tracking. When you record an AC resisted extension test, and the rest of the cluster, capture:

• Test name and date for traceability across visits
• Patient position, confirming 90 degrees shoulder flexion with internal rotation and the elbow flexed to 90 degrees
• Examiner technique, including the direction and magnitude of resistance applied
• Pain response, with location (AC joint versus elsewhere), intensity (0-10), and quality (sharp, dull, reproducible)
• Positive or negative finding as a clear binary result for comparison over time
• Associated tests, such as the cross-body adduction test, Paxinos sign, palpation, and any imaging correlation
• Clinical interpretation, including the suspected diagnosis or differentials

Practice management software like Pabau lets you store the assessment template and link it straight to the patient record, so longitudinal tracking of AC joint findings takes no extra admin. Consistent records also support audit trails and continuity when more than one clinician sees the same patient. A structured client record keeps every AC joint pain test in one timeline.

Best practices for AC joint assessment

Combine the AC resisted extension test with these practices to sharpen your assessment:

• Palpate the AC joint first, mapping tenderness and a baseline pain response before any provocation test
• Run the cluster, not one test: the cross-body adduction test, Paxinos sign, AC shear test, and resisted extension test together beat any single maneuver
• Correlate with imaging, using plain films or ultrasound to confirm what the cluster suggests
• Weigh the history: direct trauma, repetitive overhead activity, and age all shift the odds, since AC joint osteoarthritis climbs with age
• Document as you go, using the template so records stay complete and reproducible

Clinical workflow automation can prompt clinicians to complete the full cluster, so testing does not become ad hoc. Recording findings immediately after the assessment keeps them accurate and cuts documentation lag.

When to refer for imaging

A positive AC resisted extension test warrants imaging when clinical suspicion is high. Consider an X-ray, ultrasound, or MRI referral when:

• Several AC joint tests are positive together (resisted extension, cross-body adduction, and Paxinos sign)
• Palpation reproduces sharp, AC-joint-specific pain
• The history includes direct trauma to the shoulder or a graded AC joint sprain
• Symptoms persist despite 4 to 6 weeks of conservative treatment
• The picture suggests AC joint osteoarthritis (older patients, degenerative pattern)

Early imaging guides treatment and rules out other pathology. Structured clinical documentation of test results and imaging findings supports shared care with orthopedic or sports medicine colleagues.

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Conclusion

The AC resisted extension test is a quick, informative screen for acromioclavicular joint dysfunction. Good specificity, moderate sensitivity, and an easy setup make it a staple of shoulder assessment, provided you get the positioning and resistance direction right. It becomes most useful when you read it inside the AC joint provocation cluster rather than alone.

Using the template keeps every AC joint assessment recorded the same way, which supports evidence-based decisions and clean handovers between clinicians. See how Pabau supports streamlined clinical documentation and keeps your special-test findings in one patient record.

Continue your research

Need a comprehensive physical therapy assessment template? Physical therapy EMR software helps you document all special tests, client records, and treatment progress in one integrated system.

Need a template for upper-limb functional assessment? The Action Research Arm Test gives you a structured way to score arm and hand function alongside your shoulder special tests.

Referring a patient for AC joint imaging? A Doppler ultrasound report template keeps imaging findings organized alongside your special-test results.

Frequently asked questions