top of page

Acromioclavicular (AC) Joint Separation and Arthritis

What is the AC Joint?


The acromioclavicular (AC) joint is where the collarbone (clavicle) meets the top of the shoulder blade (acromion).


What is This Condition?


  • AC separation: injury to the ligaments holding the clavicle in place, often from a fall onto the shoulder.

  • AC arthritis: wear-and-tear of the AC joint cartilage, causing pain at the top of the shoulder.


What Causes It?


  • Separation: direct trauma, usually from sports or falls

  • Arthritis: gradual breakdown of cartilage from aging, overuse, or after an old injury


What are the Symptoms?


AC Separation:


  • Sudden pain on top of the shoulder after a fall or impact

  • Swelling and bruising at the AC joint

  • A visible bump where the collarbone is raised (in more severe injuries)

  • Pain with lifting the arm across the body


AC Arthritis:


  • Aching pain at the top of the shoulder, often worse with overhead lifting or cross-body movements

  • Tenderness directly over the joint

  • Stiffness or grinding when moving the shoulder


How is It Diagnosed?


  • Exam: pain at the top of the shoulder, swelling after injury, or tenderness with direct pressure

  • X-rays: show separation, arthritis, or joint space narrowing


How is It Treated?


For separations:

  • Rest, ice, and sling for mild injuries

  • Physical therapy for recovery

  • Surgery for severe separations that cause deformity or persistent pain


For arthritis:

  • Activity modification and NSAIDs

  • Cortisone injections into the AC joint

  • Surgery (distal clavicle excision) if pain continues despite non-surgical care


Learn more from AAOS (OrthoInfo):

https://orthoinfo.aaos.org/en/diseases--conditions/shoulder-separation/

bottom of page