AC Joint Separations

An AC joint separation is a ligament injury at the very top of the shoulder, where the outer end of the collarbone meets a bony shelf on the shoulder blade. When the ligaments tear, the collarbone loses its anchor and can ride upward, creating a step or bump in higher-grade injuries. The grade, which reflects how far the collarbone has shifted and which ligaments are torn, drives the treatment decision. Most people recover full shoulder strength.

Pain at the very top of the shoulder is immediate after the injury. Common symptoms include:

• Pain at the top of the shoulder, sharp right after the injury
• A visible step or bump where the collarbone sits higher, in higher-grade injuries
• Pain lifting the arm overhead or bringing it across the chest
• Discomfort sleeping on the affected side for weeks

The diagnosis is made from the history, a physical exam, and X-rays. Your provider looks for a step deformity at the top of the shoulder, tenderness over the joint, and pain when the arm is brought across the chest. In borderline cases, an X-ray taken while holding a small weight can unmask displacement and help determine the grade. An MRI is reserved for higher-grade or unusual injuries.

Mild and moderate separations, and many complete ligament tears, recover without surgery:

• A sling worn for one to a few weeks to unload the joint while the ligaments calm down
• Physical therapy with gentle motion, then strengthening of the rotator cuff and shoulder-blade muscles
• Anti-inflammatory medication for pain and inflammation during the acute weeks
• A corticosteroid injection into the joint when a milder separation leaves lasting pain

For the most severe separations, surgery is almost always needed, because the collarbone is displaced too far for the ligaments to scar back into place. Reconstruction uses a graft to pull the bone back to its normal position.

For a fuller explanation, including anatomy, diagnosis, and the full range of treatment:

• Shoulder Separation — AAOS OrthoInfo