Acromioclavicular Joint Injury



  • The acromioclavicular (AC) joint is formed by the articulation of the distal clavicle and the scapular acromion
  • It is stabilized by the AC ligament, coracoclavicular (CC) ligament, and attachments from deltoid and trapezius muscles
    • AC ligament is responsible for horizontal stability
    • CC ligament is responsible for vertical stability
  • Rockwood classification (sequential injury pattern):
    • Type I:
      • No visible deformity
      • Sprained AC ligament (AC joint tender)
      • Intact joint capsule
      • No CC ligament injury (nontender)
      • No deltoid or trapezius injury
      • No radiographic abnormality (clinical diagnosis)
    • Type II:
      • Ruptured AC ligament (AC joint tender) (distal clavicle horizontally unstable)
      • Ruptured joint capsule
      • Sprained CC ligament (CC ligament tender)
      • Minimal deltoid and trapezius injury
      • Radiographs show slight widening of AC joint (normal <5 mm)
      • Normal CC space (11–13 mm)
    • Type III:
      • Ruptured AC ligament (AC joint tender) (distal clavicle horizontally unstable)
      • Ruptured joint capsule
      • Ruptured CC ligament (CC ligament tender) (distal clavicle vertically unstable)
      • Detached deltoid and trapezius
      • Complete AC dislocation
      • Radiographs show widening of AC joint
      • Increased CC space, with distal clavicle above superior aspect of acromion (100% displaced)
    • Types IV, V, and VI:
      • Cause more significant pain than types I, II, and III
      • Best visualized on lateral/axillary radiographs
      • All require operative treatment
      • Greater risk for prolonged disability
    • Type IV:
      • Identical ligamentous/muscular injury pattern to type III
      • Clavicle is displaced posteriorly into trapezius muscle
      • Posteriorly displaced clavicle may be palpable on exam
      • May cause tenting of skin posteriorly
    • Type V:
      • Rare
      • Identical ligamentous/muscular injury pattern to type III
      • Clavicle is displaced superiorly above the trapezius (100–300% increase in CC space)
      • Shoulder droops severely
      • Clavicle may be palpated subcutaneously
      • May cause tenting, ischemia, or disruption of skin
    • Type VI:
      • Usually associated with severe trauma with multiple injuries
      • Identical ligamentous/muscular injury pattern to type III
      • Clavicle is displaced inferiorly into subacromial or subcoracoid location
      • Shoulder appears flattened
      • Associated neurovascular injury is common


  • Injury most commonly seen in young, active males during contact sports
  • Most common mechanism is direct trauma to superior or lateral shoulder while arm is adducted, usually in the setting of a fall:
    • Acromion is displaced inferomedially
    • Clavicle remains stabilized by sternoclavicular ligaments
  • May also occur indirectly via a fall on an outstretched hand or elbow, with transmission of force to the AC joint


Signs and Symptoms

  • Pain to anterior or superior aspect of the shoulder following trauma
  • Pain exacerbated by moving arm across the chest, behind the back, or overhead
  • Mechanism/force will dictate suspicion for and pattern of injury
  • Associated neurovascular symptoms
  • Cervical spine symptoms

Physical Exam
  • Exam in standing or sitting position, as supine position negates force of gravity which can mask joint instability
  • Inspection: Ecchymosis, abrasion, swelling, symmetry, deformity of AC joint, skin tenting, or laceration
    • Prominence of clavicle with sagging of the acromion indicates rupture of AC joint (Rockwood type II injury or greater)
  • Palpation: Sequential exam of sternoclavicular joint, length of clavicle, AC joint, CC ligament, coracoid process, scapular spine, and proximal humerus
    • Tenderness over AC joint indicates AC ligament injury (Rockwood type I injury or greater)
    • Horizontal instability of distal clavicle indicates AC ligament rupture (Rockwood type II injury or greater)
    • Tenderness over CC ligament indicates CC ligament injury (Rockwood type II injury or greater)
    • Vertical instability of distal clavicle indicates CC ligament rupture (Rockwood type III injury or greater)
  • Special tests:
    • Cross-body adduction test:
      • Arm elevated to 90 degrees with elbow flexed at 90 degrees, and adducted across chest
      • Pain confirms AC injury by specifically compressing the joint
      • Sensitivity 77%, specificity 79%
    • O'Brien test:
      • Arm elevated to 90 degrees with elbow in extension, adduction of 10–15 degrees and maximum forearm pronation
      • Examiner applies downward force against resistance
      • Pain over top of shoulder confirms AC injury
      • Sensitivity 16–93%, specificity 90–95%
  • Complete distal neurovascular exam, including brachial plexus
  • Careful cervical spine exam

Essential Workup

  • History to seek mechanisms that commonly cause AC joint injury and associated force
  • Physical exam to evaluate for injury pattern, neurovascular compromise and exclude other causes of pain
  • Radiographic evaluation as outlined below

Diagnostic Tests and Interpretation

  • Specific AC joint radiograph:
    • Recommended if AC injury suspected
    • Should include bilateral AC joints (for comparison)
    • Standard shoulder views will over penetrate AC joint and may obscure subtle injuries
    • Stress views no longer recommended
  • Zanca view (10–15 degrees cephalic tilt to remove scapula from field) for limited initial views
  • Axillary view for type III–VI injuries to determine position of distal clavicle
  • CT or MRI for further evaluation of surgical cases (Rockwood types IV–VI)
    • Angiography may be used to evaluate associated neurovascular injuries
    • US if CT/MRI is not available

Differential Diagnosis

  • Shoulder dislocation
  • Fractures of acromion or clavicle
  • Rotator cuff injury
  • Tendinitis
  • Capsulitis
  • Cervical radiculopathy
  • Osteoarthritis
  • Osteomyelitis

Pediatric Considerations
  • Pediatric clavicle encased in periosteal tube:
    • CC ligament within tube
    • AC ligament external to tube (more vulnerable)
  • AC joint injury rarely occurs in isolation in the pediatric population
  • When injury does occur, it is more often type I or II
  • Distal clavicular fractures through physis are more common than type III AC joint dislocations


Pre Hospital

  • Ice packs
  • Sling immobilization
  • Cervical spine immobilization if indicated

Initial Stabilization/Therapy

  • Ice packs
  • Sling immobilization
  • Cervical spine immobilization if indicated
  • Analgesia (NSAIDs, other analgesics)

Ed Treatment/Procedures

  • Types I and II:
    • Rest, ice, analgesics
    • Brief sling immobilization (typically 3–7 d)
    • Range of motion (ROM) and strengthening exercises as soon as can be tolerated
    • Resume normal activities once painless ROM and strength have returned (2–4 wk)
  • Type III:
    • Rest, ice, analgesics
    • Sling immobilization and early (within 72 hr) orthopedic referral
  • Treatment plan is controversial as insufficient evidence exists to favor one management strategy over the other (conservative vs. surgical)
    • Which approach is chosen may depend on general health of patient, level of activity, occupation, hand dominance, and risk for reinjury
    • Current trend is toward nonoperative management except for those with persistent symptoms and functional limitations after 6–12 wk
  • Types IV, V, and VI:
    • Rest, ice, analgesics
    • Sling immobilization and immediate orthopedic referral
    • Require early surgical intervention
  • Special circumstance: Potential future complication of AC joint injury is arthritis of the joint

Pediatric Considerations
  • Types I and II:
    • Conservative management (rest, ice, analgesics, sling)
    • Should heal without major sequelae
  • Type III:
    • Age <15 yr, conservative management
    • Age ≥15 yr may require more aggressive treatment
  • Types IV, V, and VI:
    • Operative repair


  • Ibuprofen: 600 mg (peds: 4–10 mg/kg) PO q.i.d
  • Ketorolac: 30 mg (peds: 0.5 mg/kg up to 30 mg if >6 mo) IM/IV q6h (15 mg IM/IV q6h if >65 yr or <50 kg)

Ongoing Care


Admission Criteria
  • Open injury
  • Types IV, V, and VI require admission for operative repair

Discharge Criteria
  • Types I and II can be discharged with orthopedic referral
  • Type III should have urgent orthopedic referral

Follow-Up Recommendations

  • Type I and II: Orthopedic follow-up within 2–4 wk
  • Type III: Early (within 72 hr) orthopedic follow-up
  • Type IV–VI: Immediate orthopedic referral
  • All pediatric injuries should have prompt orthopedic follow-up, with type IV–VI injuries requiring immediate referral

Pearls and Pitfalls

  • Type I and II AC injuries:
    • No increase in CC space
    • Conservative management with rest, ice, sling, and ROM/strength exercises
  • Type III injuries:
    • 100% superior displacement of distal clavicle
    • Management somewhat controversial
    • Require early orthopedic follow-up
  • Type IV–VI injuries:
    • Identical ligamentous and muscular injuries to type III
    • Difference according to position of distal clavicle
    • Operative management is standard of care

Additional Reading

  • Bossart PJ, Joyce SM, Manaster BJ, et al. Lack of efficacy of weighted radiographs in diagnosing acute acromioclavicular separation. Ann Emerg Med. 1988;17:47–51.
  • Bussieres AE, Peterson C, Taylor JA. Diagnostic imaging guideline for musculoskeletal complaints in adults—an evidence-based approach-part 2: Upper extremity disorders. J Manipulative Physiol Ther. 2008;31(1):2–32.
  • Hegedus EJ, Goode A, Campbell S, et al. Physical examination tests of the shoulder: A systematic review with meta-analysis of individual tests. Br J Sports Med. 2008;42:80–92.
  • Mazzocca AD, Arciero RA, Bicos J. Evaluation and treatment of acromioclavicular joint injuries. Am J Sports Med. 2007;35(2):316–329.
  • Simovitch R, Sanders B, Ozbaydar M, et al. Acromioclavicular joint injuries: Diagnosis and management. J Am Acad Ortho Surg. 2009;17:207–219.
  • Stucken C, Cohen SB. Management of acromioclavicular joint injuries. Orthop Clin N Am. 2015;46(1):57–66.
  • Tamaoki MJS, Belloti JC, Lenza M, et al. Surgical versus conservative interventions for treating acromioclavicular dislocation of the shoulder in adults. Cochrane Database of Sys Rev. 2010;(8):CD007429.

See Also


Gina T. Waight
Aleksandr M. Tichter

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