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  • Separated Shoulder
  • AC separation
  • AC dislocation
  • Shoulder separation

  • 840.0 Acromioclavicular (joint or ligament) sprain
  • 831.04 Closed dislocation of acromioclavicular (joint)
  • 831.14 Open dislocation of acromioclavicular (joint)

  • S43.109A Unspecified dislocation of unspecified acromioclavicular joint, initial encounter
  • S43.50XA Sprain of unspecified acromioclavicular joint, initial encounter


  • Inflammation, irritation, or separation of the joint between the clavicle and acromion (AC joint)
  • Three ligaments of stability
    • Acromioclavicular ligament
    • Coracoacromial ligament
    • Coracoclavicular ligament: made up of the conoid ligament and trapezoid ligament

Essentials of Diagnosis

  • Diagnosis is made by history and clinical exam and x-ray
  • Occurs most often from falling on an outstretched arm or hand
  • AC separation occurs when the ligaments are completely torn and there is a dislocation of the joint
  • Separation of the clavicle and acromion can be felt upon palpation
  • Step deformity often noticed when the clavicle is raised due to ligament tearing
  • Six grades of sprain to separation: Rockwood scale
    • Grade I
      • Slight displacement of the joint
      • Partially torn AC ligament
      • Separation < 4mm
    • Grade II
      • Partial dislocation of the joint
      • Complete disruption tear of the AC ligament
      • Partial disruption of the coracoclavicular ligament
      • Separation > 5mm
    • Grade III
      • Partial dislocation of the joint
      • Complete disruption tear of the AC ligament
      • Complete disruption/rupture of the coracoclavicular ligament
    • Grade IV
      • Dislocation of the joint
      • Posterior displacement
      • Requires surgery
    • Grade V
      • Dislocation of the joint
      • Superior displacement
      • Requires surgery
    • Grade VI
      • Dislocation of the joint
      • Inferior displacement
      • Requires surgery

General Considerations

  • No synovial joint
  • Osteoarthritis is common without treatment or with prolonged instability


  • Predominately in individuals with a history of activities involving overhead reach: swimming, tennis, and baseball as well as with occupational activities involving repetitive overhead activity

Signs and Symptoms

  • Ache in the anterior top aspect of the shoulder
  • Frequently worsens with overhead lifting or activity
  • Pain with palpation at AC joint
  • Step deformity of the clavicle and acromion
  • Occasional sound or sensation of snapping
  • Pain with traction on the arm

Functional Implications

  • May limit overhead activities, especially lifting
  • May limit throwing and other rapid arm movements

Possible Contributing Causes

  • Frequent and prolonged overhead activity
  • Prolonged repetitive use of the involved arm
  • Poor posture (i.e., rounded shoulders)
  • Anterior displacement of the humeral head
  • Rotator cuff weakness
  • Fall on outstretched hand
  • Landing on lateral tip of the acromion

Differential Diagnosis

  • Rotator cuff tendinitis
  • Rotator cuff impingement
  • Rotator cuff tear
  • Subacromial bursitis
  • Bicep tendinopathy
  • Bicep tear
  • Labral tear


  • Radiographs while patient ...

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