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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


  • 4E: Impaired Joint Mobility, Motor Function, Muscle Performance, and Range of Motion Associated with Localized Inflammation1


A 53-year-old woman presents with 8/10 pain in the left shoulder after a bicycle accident 2 days ago. The patient states she fell off of her bike onto her outstretched arm during the “sprint” phase of interval training on the road. The patient complains of pain in the top aspect of her left shoulder and is unable to lift her left arm. The patient also states she hears a snapping sound if attempting to move her shoulder. Upon palpation, the patient reports severe pain in the acromioclavicular joint and a significant step deformity is present. Inflammation is present throughout the entire acromioclavicular joint. The Full Can/Empty Can, Neer, and Yergason tests are negative. The Acromioclavicular Resisted Extension Test is positive.



  • Inflammation, irritation, or separation of the joint between the clavicle and acromion (AC joint)2

  • Three ligaments of stability:

    • Acromioclavicular ligament2

    • Coracoacromial ligament

    • Coracoclavicular ligament: Made up of the conoid ligament and trapezoid ligament2

Essentials of Diagnosis

  • Patient history and clinical examination

  • 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

  • Look for separation of the clavicle and acromion

  • 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 <4 mm

    • Grade II

      • Partial dislocation of the joint

      • Complete disruption tear of the AC ligament

      • Partial disruption of the coracoclavicular ligament

      • Separation >5 mm

    • 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

  • Not a 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

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