Acromioclavicular (ACJ) Arthritis

ACJ Arthritis

Summary

  • Osteoarthritis of the Acromioclavicular joint
  • The AC joint can become a source of pain in the shoulder, because of:
  • Diagnosis
    • Pain on palpation,
    • reproduction of pain with cross-body adduction
    • diagnostic injections
    • Plain radiographs
      • Zanca view,
  • Treatment
    • Nonoperative management
      • can be successful,
    • Operative
      • distal clavicle resection

Aetiology

  • idiopathic
    • elderly
      • Degenerative osteoarthritis is more common with advanced age
      • AC joint arthritis is much less common than hip, knee, or glenohumeral arthritis
  • trauma
    • young
      • Posttraumatic arthritis is a more common cause than primary osteoarthritis
  • Distal clavicle osteolysis
    • less-common cause, occurs in certain power athletes (e.g., weight-lifters).

Epidemiology

  • Common cause of superior shoulder pain in middle aged and older adults
  • Radiographic degeneration very common after 40 years, often asymptomatic
  • Post traumatic arthritis after ACJ injury or distal clavicle fracture
  • Distal clavicle osteolysis in young weightlifters
  • Coexists with subacromial impingement and rotator cuff disease

Anatomy

  • The AC joint is a hyaline cartilage joint with a fibrocartilage meniscal disc.

Pathology

  • Disc starts to break down with normal ageing and, by early adulthood, is minimal
  • Disc may be injured with an AC separation or with repetitive activity

Classification

4 patterns

PatternNotes
DJD with osteophytesContribute to impingement
OsteolysisWith resorption & gross osteoporosis, due to repetitive microtrauma (eg weight lifters)
RA
Hyperparathyroidism

History

  • Pain:
    • anterosuperior shoulder pain
    • worse with activities that load the joint (reaching across shoulder, behind body, bench-press)
    • Night pain: difficulty sleeping on affected side
    • pain radiates to trapezius > spasm

Examination

  • Direct Palpation
    • Tenderness to direct palpation
      • is most reliable sign
    • may feel osteophytes
  • Provocative tests
    • horizontal adduction of arm (tends to overlap with impingement)
    • max IR of shoulder (more sensitive & specific)
  • Injection of local anaesthetic
    • useful

Investigations

Acromioclavicular Joint Dislocation, radiograph of a rockwood type iii acromioclavicular joint dislocation
Radiograph of a Rockwood type III acromioclavicular joint dislocation. Image by Hellerhoff, Wikimedia Commons, CC BY-SA 3.0.

X-ray

  • AP Shoulder
    • neutral
    • IR
    • ER (true AP)
  • AP with 10° cephalic tilt with 1/3 penetration [zanca view]
    • best for AC joint
  • Look for
    • sclerosis
    • subchondral cysts
    • joint space narrowing
    • osteophyte formation
    • bone loss at distal clavicle (osteolysis)

Bone Scan

  • increased uptake in joint

MRI

  • very helpful
  • can be difficult to determine signal because of Normal age related changes

Lignocaine Injection

  • Local anaesthetic injected into the ACJ, often with corticosteroid
  • Pain relief confirms the ACJ as the pain source
  • Palpation guided injection often misses the joint, US guidance improves accuracy
  • Separate subacromial injection helps distinguish coexisting pathology
  • Positive response predicts good outcome from distal clavicle excision

Differential Diagnosis

Treatment

Principles

  • Most can be treated nonoperatively

Non-operative

  • most respond to Non-operative management
    • NSAIDs
    • Activity modification
      • Limitation of exacerbating activities such as bench-presses, dips, push-ups, and overhead activities
    • Steroid injection
    • Physiotherapy: minimal role
  • consider operative management after 6 months

Operative

  • Indication
    • if fail nonoperative management
  • 90% success rate
  • resect 1cm – 2cm (to prevent continued bony contact between the clavicle and acromion)
  • Options
    • Open resection
    • Arthroscopic
      • preserves AC capsule
      • quicker rehabilitation
  • Complications
    • incomplete resection
    • continued pain after surgery
    • excessive resection leading to distal clavicle instability

Prognosis

  • Most respond to activity modification, analgesia and injection
  • Good to excellent results in most patients after distal clavicle excision
  • Open and arthroscopic excision give comparable results, arthroscopic recovery is quicker
  • Over resection or AC ligament injury causes instability and residual pain
  • Poorer results in post traumatic cases and with coexisting pathology

Reviewed by Professor Phong Tran, Head of Orthopaedic Surgery, Western Health. Last updated 10 October 2026.