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    Acromioclavicular Joint Separation

    Orthopedic, Trauma

    Last Updated Jun 10, 2021
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    By David Barbic, Ryan Koo


    Most commonly occur with a direct blow to the shoulder. 9-12% of shoulder injuries have Acromioclavicular (AC) joint involvement.

    • Peak incidence is ages of 20-29, most commonly males who play contact sports.
    • The majority of patients with an isolated, low-grade (Type I-III) AC separation can be discharged home and managed on an outpatient basis.
    • Higher grade separations (Type IV-VI) may require surgical repair.

    Diagnostic Process


    • Direct lateral or superior blow to the acromion, usually with the arm in an adducted position.
    • Less commonly with a fall on outstretched hand (FOOSH) injury.
    • Pain, deformity, or instability over the AC joint, worsened by arm elevation.


    • Rule out brachial plexus involvement – cervical spine screen, distal neurological and vascular examination.
    • Rule out injury to associated structures via palpation (Sternoclavicular joint, clavicle, acromion, scapula, coracoid process, humerus).
    • Swelling and tenderness located at the AC joint; deformity, prominence or displacement of the clavicle may be noted in higher-grade injuries.

    If the injury is mild and diagnosis unclear, special testing can be performed (see Related Information for videos):

      • Cross-body adduction test (77% sensitivity, 79% specificity).
        • Passively hold the patient’s straight arm at 90 degrees of shoulder flexion, in neutral rotation; then passively horizontally adduct across the patient’s body.
        • A positive test is indicated by the reproduction of pain.

    Source: Musculoskeletal Key


    O’Brien (active compression) test (41% sensitivity; 94% specificity).

      • Instruct patient to flex shoulder to 90 degrees, and horizontally adduct by 10-15 degrees.
      • Passively internally rotate the arm maximally, and ask the patient to resist an inferiorly directed force (positive test = provocation of pain).
      • Repeat with arm in an externally rotated position (pain should be reduced/absent).

    Source: BMJ (https://bjsm.bmj.com/content/42/8/628).



    • Suspected AC joint injury should initially be evaluated with a plain x-ray.
    • Stress (weighted) views are no longer recommended due to limited diagnostic value and pain.


    • Ultrasound or MRI for detailed evaluation are typically ordered on an outpatient basis – not an ED order.
    • Evaluation with CT is not recommended.


    Created by Ella Barrett-Chan, UBC MSI3, 2023

    Recommended Treatment

    Conservative Management

    • Rest, ice, and analgesics PRN.
    • Shoulder immobilization (see below for specific recommendations by injury type).
    • Shoulder range of motion exercises as soon as tolerated to minimize the risk of adhesive capsulitis.
    • Referral to primary care physician and/or physiotherapy for ongoing management.

    Management by Injury Type

    Type I-II

    • Conservative management.
    • Sling for <3-7 days.
    • Recovery timelines: Type I = 1-2 weeks; Type II = 3-4 weeks.

    Type III

    • Urgent referral (3-7 days) to orthopedics indicated for consideration of operative repair, though conservative management usually adequate.
    • Sling for <2-3 weeks.
    • Recovery timeline: 6-12 weeks.

    Type IV-VI

    • Requires referral for orthopedic evaluation for consideration of operative repair.
    • If neurovascular compromise is present, referral should be emergent.
    • Prognosis variable.

    Quality Of Evidence?


    Low-to-moderate. Management of low-grade and high-grade AC joint injuries have widely consistent management recommendations, but criteria for surgical management is debated.


    Related Information

    Reference List

    Relevant Resources


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    Shoulder Dislocation (Cunningham Method)

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