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Acromioclavicular Joint Separation

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Other Names

  • Shoulder Separation
  • Shoulder Sprain
  • AC Sprain
  • AC Joint Sprain
  • AC Dislocation
  • Acromioclavicular Joint Dislocation


  • This page refers to all traumatic injuries to the Acromioclavicular Joint including
    • Sprains
    • Dislocations
    • Separations


  • Thought to be under-estimated due to many mild injuries not seeking medical attention
  • Represents 9% of all shoulder injuries (need citation)
  • 50% of all AC dislocations occur to individuals in their 20s (need citation)
  • Types 1 and 2 injuries account for most AC separations


  • Mechanism of injury is primarily by direct impact over the AC joint
    • From fall or contact sport
    • Arm is adducted


  • Many causes
    • Simple falls
    • High energy trauma
    • Sports


Associated Injuries

Risk Factors

  • Male > Female
  • Sports
    • Contact and collision sports
    • Skiing
    • Cycling

Differential Diagnosis

Clinical Features

  • General: Physical Exam Shoulder
  • History
    • Patient should describe some trauma
    • Shoulder pain at or close to AC joint
  • Physical
    • Most commonly, tenderness over AC joint
    • Inspection may show asymmetry of shoulders or swelling at the AC joint
    • Range of Motion is usually reduced due to pain acutely
    • Pain with adduction of the shoulder and possibly with shoulder abduction and flexion
    • Deformity (step-off) of AC joint with type III injuries and higher
    • Type III and V may show instability of the lateral clavicle when depressed manually ("piano key" phenomenon)
  • Special Tests



  • Standard Radiographs Shoulder
  • Zanca view (sometimes referred to as the AC joint view)[2]
    • Beam is tilted cephalic 10 - 15°
    • Provides superior AC joint evaluation
    • Recommend bilateral evaluation for comparison
    • The average distance between the inferior aspect of the clavicle and the coracoid is 1.1 to 1.3 cm
  • Basmania view: scapular Y performed with cross-body adduction stress
  • Stryker notch views can assess for coracoid fracture
  • Note: Weighted stress views are no longer used


  • CT has not been shown to improve diagnostic yield


  • Can directly assess AC and CC ligaments
  • Useful if surgical intervention is being considered


  • Can be used to evaluate the AC joint


Rockwood Classification of Acromioclavicular Injuries

Type AC Ligaments CC Ligaments Deltopectoral Fascia CC Distance AC Joint (Xray)
I Sprained Intact Intact Normal Normal
II Disrupted Sprained Intact <25% Widened
III Disrupted Disrupted Disrupted 25%-100% Widened
IV Disrupted Disrupted Disrupted Increased Posterior displaced clavicle
V Disrupted Disrupted Disrupted 100-300% N/A
VI Disrupted Disrupted Disrupted Decreased Inferior displaced clavicle


Types I and II

  • Universally nonoperative
  • Analgesia with ice, NSAIDS, Acetaminophen, et
  • Immobilization: Shoulder Sling
    • Discontinue once asymptomatic
    • Type I: Typically 1-3 weeks
    • Type II: Longer, up to 4 weeks[3]
  • Activity modification
    • Type II injuries may require early rehabilitation program with passive and active shoulder ROM exercises
    • Rotator cuff, scapular stabilization, and trunk strengthening exercises as pain resolves
    • Heavy lifting and contact activities only once extremity is pain free and symmetric ROM is acheived
  • Consider Corticosteroid Injection in refractory cases

Type III

  • Management is controversial
    • Not a lot of high level evidence to guide decision making
    • General consensus is to advocate for initial nonoperative management.
    • Individualized treatment based on patient activity level, impairment, and occupation
    • Consider surgical repair in acute, young patients
    • Comparably high satisfaction with operative and nonoperative treatment though higher complication rates in those treated surgically[4]
  • Nonoperative treatment
    • Similar to Type I, II

Type IV - VI

  • Generally considered surgical
  • Technique
    • Many described in literature
    • ORIF most common

Rehab and Return to Play


  • Needs to be updated

Return to Play

  • Return to play once pain completely resolved and equal active ROM in bilateral shoulders. Followed by adequate strength training.
  • Recovery generally takes 6 weeks for Type II injuries and 12 weeks for Type III injuries


See Also


  1. . Tischer T, Salzmann GM, El-Azab H, Vogt S, Imhoff AB. Incidence of associated injuries with acute acromioclavicular joint dislocations types III through V. Am J Sports Med. 2009 Jan;;37(1):136-9. Epub 2008 Aug 25.
  2. Zanca P. Shoulder pain: involvement of the acromioclavicular joint. (Analysis of 1,000 cases). Am J Roentgenol Radium Ther Nucl Med. 1971 Jul;112(3):493-506.
  3. Park JP, Arnold JA, Coker TP, Harris WD, Becker DA. Treatment of acromioclavicular separations. A retrospective study. Am J Sports Med. 1980 Jul-Aug;8(4):251-6
  4. Glick JM, Milburn LJ, Haggerty JF, Nishimoto D. Dislocated acromioclavicular joint: follow-up study of 35 unreduced acromioclavicular dislocations. Am J Sports Med. 1977 Nov-Dec;5(6):264-70.
  5. Mouhsine E, Garofalo R, Crevoisier X, Farron A. Grade I and II acromioclavicular dislocations: results of conservative treatment. J Shoulder Elbow Surg. 2003 NovDec;12(6):599-602.
Created by:
John Kiel on 4 July 2019 08:23:12
Last edited:
11 October 2023 16:15:30