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Condition/Disorder Synonyms

  • Separated Shoulder

  • AC separation

  • AC dislocation

  • Shoulder separation

ICD-9-CM Code

  • 840.0 Acromioclavicular (joint or ligament) sprain

  • 831.04 Closed dislocation of acromioclavicular (joint)

  • 831.14 Open dislocation of acromioclavicular (joint)

ICD-10-CM Code

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

  • S43.50XA Sprain of unspecified acromioclavicular joint, initial encounter

Preferred Practice Pattern1

Key Features


  • 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

Clinical Findings

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 ...

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