AC joint separation: symptoms, treatment, and when to worry
Last updated September 3, 2026.
An AC joint separation is an injury at the top of your shoulder, where the collarbone meets the shoulder blade. A fall onto the shoulder or a direct blow tears the ligaments holding that joint together. It is not the same as a shoulder dislocation, which is the arm bone coming out of the main shoulder socket.
What does it look like?
Pain sits right on top of the shoulder, often with swelling and tenderness over the joint. In bigger tears the end of the collarbone sticks up, creating a visible bump, or the shoulder hangs lower than the other side. Reaching across your body, lying on that side, and lifting overhead usually hurt the most. Clinicians grade separations by how far the collarbone has shifted, from a mild sprain with a normal X-ray to fully torn ligaments with displacement.
What actually helps?
- Sling and ice first: support the arm in a sling and ice the joint wrapped in a cloth to bring down swelling, with regular simple pain relief.
- Move gently, early: most AC injuries are treated without surgery, and progressive gentle movement as pain allows beats prolonged immobilization.
- Physio to rebuild: exercises restore range of motion, then strengthen the shoulder blade and rotator cuff before a gradual return to sport or heavy work.
- Surgery is the exception: it is considered for rare, severely displaced injuries, usually from high-energy trauma, and your surgeon would talk you through it.
- Expect the bump to fade or stay: milder injuries settle completely; bigger tears can leave a painless permanent bump even after full function returns.
When is it an emergency?
Most AC separations can wait for a same-day or next-day assessment rather than an ambulance. Get urgent care now if, after the injury, the arm or hand is numb, cold, or changing color, the collarbone end is tenting or breaking the skin, there is an open wound over the joint, or pain is severe and uncontrolled. Those signs suggest a fracture, a badly displaced injury, or nerve or blood vessel damage. Pymander's escalation routing is built and tested specifically for this class of decision; see the safety architecture working paper.
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Common questions
What is the difference between an AC joint separation and a shoulder dislocation?
They involve different joints. An AC separation is at the very top of the shoulder, where the collarbone meets the shoulder blade, and it typically causes a bump there. A dislocation is the ball of the upper arm bone coming out of the main shoulder socket, which makes the whole shoulder look out of place and stops you moving the arm. Both follow falls and collisions, but they are treated differently.
How long does an AC joint separation take to heal?
Mild sprains often settle over a few weeks, while more severe tears take longer, commonly six to twelve weeks before a full return to contact sport or heavy lifting. Most people wean out of the sling as comfort allows and rebuild strength with physiotherapy. The timeline depends on the grade of the tear, which is why an exam and usually an X-ray come early.
Will the bump on my shoulder go away?
That depends on the grade. Mild separations heal without any lasting change. In bigger tears where the collarbone has shifted upward, a small bump often remains even after the pain and weakness are gone. It looks odd but usually works fine, and most people with a residual bump return to full activity without surgery.
Do I need surgery for an AC joint separation?
Most people do not. Sling support, pain relief, and physiotherapy handle the large majority of these injuries. Surgery is reserved for the uncommon, severely displaced injuries, typically from high-energy trauma, or for persistent problems after conservative treatment. If surgery is on the table, your surgeon will explain why your specific injury warrants it.
When can I go back to sport after an AC separation?
When you have full, pain-free range of motion and strength back, and contact athletes usually add a margin for the bump to stop being tender to direct hits. Rushing back risks re-injury of the healing ligaments. Your physio or doctor clears the return based on function rather than time elapsed.
Can an AC separation cause problems years later?
Some people develop arthritis in the AC joint years after a separation, showing up as aching on top of the shoulder with overhead or cross-body movements. Most people have no long-term trouble at all. If late aching develops, it is usually managed with activity changes, physio, and sometimes an injection rather than anything drastic.