Shoulder Orthopaedic Test: AC Shear Test

The AC Shear Test is a shoulder special test used to provoke symptoms at the acromioclavicular joint by applying a shear or compression force between the clavicle and scapular/acromial region. It is commonly used when AC joint pain, irritation or local instability is part of the assessment reasoning.

A positive finding may include familiar local AC joint pain, abnormal movement, apprehension or clear side-to-side difference. However, diagnostic accuracy evidence for the exact AC Shear Test appears limited, so the result should be interpreted alongside history, trauma mechanism, AC joint palpation, cross-body adduction, Paxinos sign, O’Brien’s active compression test, range of motion, strength and imaging where relevant.

Introduction

The AC Shear Test is used to assess symptom response around the acromioclavicular joint, commonly called the AC joint. The AC joint is the small joint between the lateral clavicle and the acromion of the scapula. It can be irritated by direct trauma, repetitive loading, falls onto the shoulder, pressing movements, overhead sport or degenerative change.

The test applies a local shear or compression force across the AC joint. If this reproduces familiar pain directly over the AC joint, the finding may support assessment reasoning that the AC joint is relevant to the client’s shoulder symptoms.

However, the AC Shear Test should not be used as a stand-alone diagnostic test. Local shoulder pain can be influenced by AC joint irritation, rotator cuff-related pain, subacromial-region symptoms, cervical referral, glenohumeral symptoms and other contributors.

For Measurz users, the value of the AC Shear Test is in recording a clear response: side tested, local pain location, pain score, whether symptoms were familiar, movement response, side-to-side comparison and related shoulder findings.

Quick Summary

Test name: AC Shear Test
Region: Shoulder / acromioclavicular joint
Primary purpose: Provoke local AC joint symptoms or movement response
Commonly associated presentations: AC joint pain, AC sprain, AC joint irritation, shoulder pain after direct trauma, pain with cross-body or pressing movements
Positive finding: Familiar local AC joint pain, abnormal movement, apprehension or clear side-to-side difference
Negative finding: No familiar AC joint pain and no meaningful side-to-side difference
Main limitation: Diagnostic accuracy evidence for the exact test appears limited.

What Is the AC Shear Test?

The AC Shear Test is a local shoulder provocation test for the acromioclavicular joint.

The professional places one hand near the clavicle and the other near the scapular spine or acromion region. A compressive or shearing force is applied to stress the AC joint.

The test may be performed in sitting or standing.

The result is based on:

• Local AC joint pain
• Familiar symptom reproduction
• Apprehension
• Abnormal movement
• Side-to-side difference
• Symptom quality

It is best used as part of an AC joint test cluster rather than alone.

Why It Is Used

The AC Shear Test may be used to support assessment reasoning around:

• Local AC joint pain
• Shoulder pain after direct trauma
• AC joint sprain-type presentations
• Pain with cross-body adduction
• Pain with pressing or overhead activity
• AC joint tenderness
• Suspected AC joint irritation
• Local shoulder pain mapping
• Side-to-side comparison
• Baseline and retest documentation

It can help determine whether direct AC joint loading reproduces the client’s familiar symptoms.

What It Assesses

The AC Shear Test assesses symptom response to local AC joint shear or compression.

It may provide information about:

• Local AC joint tenderness
• Familiar pain reproduction
• AC joint irritability
• Apprehension with AC joint loading
• Abnormal local movement
• Side-to-side difference
• Tolerance to local shoulder loading

It does not directly assess:

• AC ligament integrity with certainty
• Coracoclavicular ligament integrity with certainty
• Radiographic AC separation grade
• Rotator cuff integrity
• Labral integrity
• Cervical contribution
• Shoulder strength
• Functional capacity
• Readiness for sport or work
• Treatment need

Who It Is Useful For

The AC Shear Test may be useful for clients with:

• Local pain over the AC joint
• Shoulder pain after a fall onto the shoulder
• Pain after contact sport trauma
• Pain with cross-body adduction
• Pain with push-ups, bench press or dips
• Pain with overhead or pressing tasks
• Suspected AC joint irritation
• Need for baseline and retest documentation

It may also be useful for professionals learning how to differentiate local AC joint symptoms from broader shoulder pain presentations.

When to Use This Test

Consider using the AC Shear Test when:

• Pain is localised near the AC joint
• The mechanism involved direct shoulder trauma
• AC joint tenderness is present
• Cross-body adduction reproduces symptoms
• Pressing or overhead activity provokes superior shoulder pain
• You want to compare side-to-side AC joint irritability
• You are building a broader shoulder assessment profile

The test should be combined with history, palpation, range of motion, strength assessment and other shoulder special tests.

When Not to Use or When to Be Cautious

Use caution or avoid the test when:

• Recent major trauma suggests fracture or significant AC separation
• There is visible deformity after acute injury
• Pain is severe before testing
• The client cannot tolerate local pressure
• Infection, inflammatory flare or systemic red flags are suspected
• The professional cannot apply the test safely
• The test would not change assessment reasoning

Stop the test if pain increases sharply, the client becomes distressed, or the test reproduces symptoms beyond a useful level.

Equipment Required

The AC Shear Test usually requires no equipment.

Optional equipment includes:

• Measurz app
• Pain rating scale
• Notes field for pain location and comparison side
• Shoulder range of motion record
• Strength testing record
• Video or image record only where appropriate
• Referral or imaging notes if relevant

Step-by-Step Protocol / Practice

Setup

Ask the client to sit or stand comfortably.

Explain the test:

“I am going to apply gentle pressure around the top of your shoulder to see whether it reproduces your familiar symptoms around the AC joint.”

Expose or identify the top of the shoulder enough to locate the clavicle, acromion and scapular spine.

Client position

The client sits or stands upright with:

• Shoulder relaxed
• Arm resting by the side
• Neck relaxed
• No active bracing
• Both shoulders visible for comparison if possible

Examiner/professional position

The professional stands behind or slightly beside the client.

They should be able to place one hand over the clavicular region and the other over the scapular spine/acromion region.

Hand placement

A common method is:

• One hand contacts the clavicle/anterior shoulder region.
• The other hand contacts the scapular spine/posterior shoulder region.
• The hands are positioned to apply a compressive or shearing force across the AC joint.

Avoid direct excessive pressure on sensitive tissue.

Stabilisation

The client remains relaxed.

Do not force the shoulder into elevation or cross-body position unless using a different AC joint test.

Movement or force direction

Apply a gentle compressive or shearing force through the AC joint region.

The force should be:

• Controlled
• Gradual
• Symptom-limited
• Compared with the other side where appropriate

Instructions

Tell the client:

“Tell me if this reproduces your familiar shoulder pain. Point to where you feel it and rate the discomfort.”

Positive finding

A positive finding may include:

• Familiar local pain directly over the AC joint
• Reproduction of the client’s usual superior shoulder pain
• Apprehension with local AC loading
• Abnormal local movement compared with the other side
• Clear side-to-side difference
• Pain that matches other AC joint findings

Record whether the finding was pain, movement, apprehension or a combination.

Negative finding

A negative finding may include:

• No familiar AC joint pain
• No meaningful side-to-side difference
• No local apprehension
• No relevant symptom reproduction
• Only mild non-familiar pressure discomfort

A negative finding does not fully exclude AC joint involvement.

Stopping criteria

Stop the test if:

• Pain increases sharply
• The client asks to stop
• There is visible acute deformity or concerning instability
• The test is too irritable to interpret
• The professional feels further testing is inappropriate

Safety notes

The test should be gentle. Avoid aggressive compression, especially after recent trauma or suspected AC separation.

Positive and Negative Test Interpretation

A positive AC Shear Test may increase suspicion that the AC joint is relevant when it reproduces familiar local pain directly over the AC joint. The finding is more meaningful when it matches the history, local tenderness, cross-body symptoms, pressing pain and other AC joint tests.

However, a positive AC Shear Test does not confirm AC joint pathology. Local pain may be influenced by soft tissue sensitivity, recent trauma, shoulder irritability, cervical referral or broader shoulder conditions.

A negative AC Shear Test may reduce suspicion that direct local AC joint shearing is a major symptom driver in that session. However, a negative result does not fully exclude AC joint involvement, particularly if other AC joint tests are positive or symptoms occur only during higher-load tasks.

The result is more meaningful when interpreted with:

• Mechanism of injury
• Pain location
• AC joint palpation
• Cross-body adduction
• Paxinos sign
• O’Brien’s active compression test
• Shoulder range of motion
• Resisted AC joint extension
• Rotator cuff tests
• Cervical assessment where relevant
• Imaging or referral findings where appropriate

Sensitivity, Specificity and Diagnostic Accuracy

At the time of writing, high-quality diagnostic accuracy evidence for the exact AC Shear Test variation appears limited.

This means the AC Shear Test should be used as a local symptom provocation and assessment reasoning tool rather than as a stand-alone diagnostic test.

Related AC joint diagnostic accuracy evidence includes:

Condition or presentation: Acromioclavicular joint pain
Population: People with shoulder pain in diagnostic accuracy studies
Test variation: AC tenderness, Paxinos test, O’Brien’s active compression and related AC joint clinical tests
Reference standard: AC joint diagnostic injection in key studies
Reported values: In Walton et al., AC tenderness had high sensitivity at approximately 96%, while the Paxinos test had sensitivity around 79%, but many tests had low specificity
Cluster evidence: A systematic review by Krill et al. reported that clinical test combinations may improve reasoning compared with individual tests, but diagnostic accuracy remains limited
Key limitation: These values are not specific to the AC Shear Test and should not be applied directly as its sensitivity or specificity.

Plain-language interpretation:

• A positive AC Shear Test may support AC joint assessment reasoning when symptoms are local and familiar.
• The exact test does not have strong diagnostic accuracy evidence.
• Related AC joint tests are more useful as a cluster than individually.
• A negative AC Shear Test does not fully exclude AC joint involvement.
• The result should be recorded descriptively rather than treated as diagnostic confirmation.

Reliability and Validity

Reliability evidence for the exact AC Shear Test appears limited.

Reliability may be affected by:

• Hand placement
• Force direction
• Amount of compression
• Client irritability
• Recent trauma
• Local tenderness
• Definition of a positive result
• Whether pain or movement is recorded
• Professional experience

Validity is limited as a stand-alone diagnostic test. The AC Shear Test has practical face validity as a local AC joint provocation test, but it does not directly verify ligament injury, joint degeneration or radiographic separation.

Reliability improves when the professional standardises:

• Client position
• Hand placement
• Force direction
• Force intensity
• Symptom questions
• Side-to-side comparison
• Pain location recording
• Positive-test criteria

Common Errors and Limitations

Common errors include:

• Applying too much pressure
• Not identifying the AC joint clearly
• Not recording symptom location
• Counting general shoulder pain as a clear positive
• Not comparing sides
• Using the test after significant trauma without caution
• Not combining with other AC joint tests
• Assuming positive pain confirms AC pathology
• Ignoring cervical or rotator cuff contribution

Limitations include:

• Exact diagnostic accuracy evidence is limited
• Local pressure can provoke non-specific pain
• It does not grade AC separation
• It does not confirm ligament integrity
• Acute trauma may require further assessment
• It should not be used alone for decision-making
• Shoulder pain sources often overlap

Practical Applications

The AC Shear Test may be useful for:

• Local AC joint symptom provocation
• Shoulder pain mapping
• Comparing sides
• Recording AC joint irritability
• Supporting broader AC joint assessment reasoning
• Baseline and retest documentation
• Client education
• Deciding whether further shoulder assessment is needed

In Measurz, it can be recorded alongside AC tenderness, Cross-Body Adduction Test, Paxinos Sign, O’Brien’s active compression test, Resisted AC Joint Extension Test, shoulder range of motion, rotator cuff testing and cervical screening.

How to Record This in Measurz

Record:

• Test name: AC Shear Test
• Side tested
• Result: positive, negative, unclear or unable to test
• Pain score
• Symptom location
• Whether pain was directly over the AC joint
• Whether symptoms were familiar
• Apprehension
• Abnormal movement if present
• Force direction
• Client position
• Comparison side
• Irritability
• Guarding or compensations
• Reason for stopping if relevant
• Related findings
• Confidence in interpretation
• Further assessment or referral notes if appropriate
• Retest date if relevant

Recording these details improves repeatability, communication, client education, assessment reasoning, monitoring over time, team consistency and reporting quality.

Related Tests / Internal Links

• Cross-Body Adduction Test
• Paxinos Sign
• O’Brien’s Active Compression Test
• Resisted AC Joint Extension Test
• AC Joint Palpation
• Shoulder Range of Motion
• Drop Arm Test
• Internal Rotation Lag Sign
• Scapular Assistance Test
• Cervical Quadrant Test

FAQs

What does the AC Shear Test assess?

It assesses local symptom response to shear or compression across the acromioclavicular joint.

What is a positive AC Shear Test?

A positive finding may include familiar local pain over the AC joint, apprehension, abnormal movement or a clear side-to-side difference.

Does the AC Shear Test diagnose AC joint injury?

No. It may support suspicion, but it does not confirm AC joint injury or pathology on its own.

Is diagnostic accuracy evidence available for this exact test?

High-quality diagnostic accuracy evidence for the exact AC Shear Test appears limited.

What should pain location be?

Pain directly over the AC joint is more meaningful than vague general shoulder pain.

Should the test be used after acute trauma?

Use caution. Significant trauma, deformity or severe pain may require further assessment before provocative testing.

Should both sides be tested?

Yes, side-to-side comparison can improve interpretation when safe and appropriate.

What should it be combined with?

History, local palpation, cross-body adduction, Paxinos sign, O’Brien’s active compression test, resisted AC joint extension and broader shoulder assessment.

Key Takeaways

The AC Shear Test provokes local AC joint symptoms using shear or compression.

A positive finding is most meaningful when it reproduces familiar local pain over the AC joint.

Diagnostic accuracy evidence for the exact AC Shear Test appears limited.

Related AC joint tests are usually more useful as a cluster than individually.

The test does not confirm AC joint pathology, ligament injury or separation grade on its own.

Measurz recording should include side, pain location, pain score, symptom familiarity, movement response and comparison side.

References

Chronopoulos, E., Kim, T. K., Park, H. B., Ashenbrenner, D., & McFarland, E. G. (2004). Diagnostic value of physical tests for isolated chronic acromioclavicular lesions. The American Journal of Sports Medicine, 32(3), 655–661. https://doi.org/10.1177/0363546503261723

Krill, M. K., Rosas, S., Kwon, K., Dakkak, A., Nwachukwu, B. U., & McCormick, F. (2018). A concise evidence-based physical examination for diagnosis of acromioclavicular joint pathology: A systematic review. The Physician and Sportsmedicine, 46(1), 98–104. https://doi.org/10.1080/00913847.2018.1413920

Walton, J., Mahajan, S., Paxinos, A., Marshall, J., Bryant, C., Shnier, R., Quinn, R., & Murrell, G. A. C. (2004). Diagnostic values of tests for acromioclavicular joint pain. The Journal of Bone and Joint Surgery. American Volume, 86-A(4), 807–812.

Cadogan, A., McNair, P. J., Laslett, M., Hing, W. A., & Taylor, S. (2013). Shoulder pain in primary care: Diagnostic accuracy of clinical examination tests for non-traumatic acromioclavicular joint pain. BMC Musculoskeletal Disorders, 14, 156. https://doi.org/10.1186/1471-2474-14-156