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Acromio-Clavicular Diastasis


Acromio-clavicular diastasis is a medical term that defines a slightly enlarged acromioclavicular joint. Also known as the AC joint, the injury occurs with a partial or complete tearing of the ligaments found near the top of the shoulder where the clavicle or collarbone meets the upper end or acromion of the scapula, or shoulder blade. This enlarged space may also be called a joint separation.


  • Contact sports injuries
  • Falls
  • Traumatic accidents or blunt force trauma


  • Pain and tenderness
  • Swelling ( in the case of grade 2 or 3 separations)
  • Bruising
  • Limited range of motion
  • Obvious or palpable bump on the shoulder


Your doctor will perform a complete oral and physical examination and history. Typically, diagnoses are made through physical exam but you may also receive x-rays to confirm diagnosis. Separations of the AC joint are classified as:

  • Grade 1 - mild or simple sprain
  • Grade 2 - a tear or sprain in an AC ligament
  • Grade 3 - complete tear in both the AC and coracoclavicular ligaments


  • Rest
  • Pain medication
  • Shoulder sling
  • Surgery


For severe AC joint separations or those designated as Grade 3 separations or tears, surgery may be indicated to repair (through suturing and screw supports) the completely torn tendon. Those who have experienced an AC injury or separation may expect slight weakening of the shoulder joint. Even those who have undergone surgery find that they need to have the joint ligaments repaired again in the future. Some experience osteoarthritis or arthritic joint symptoms within a couple of years of the injury.