AC joint injury
Content reviewed by✓Mr Andrew Davies, PhD FRCS (Tr & Orth)· Reviewed June 2026An injury to the small joint at the top of the shoulder, where the collarbone meets the shoulder blade. Injuries range from a minor sprain of the ligaments to a complete separation of the joint. Most heal without surgery.
📊 AC joint injuries are common in contact sports and cycling. They make up around 1 in 10 of all shoulder injuries seen in hospital, and a higher proportion in sports such as rugby and mountain biking.
What is an AC joint injury?
The AC joint sits at the very top of the shoulder, where the end of the collarbone meets a small bony point on the shoulder blade. Strong ligaments hold the two bones together. A fall directly onto the point of the shoulder, or a heavy blow, can stretch or tear these ligaments.
Doctors grade these injuries from milder (just a sprain of the ligaments) to more severe (the joint completely separates and you can see a step or bump on top of the shoulder). Milder injuries are treated with rest, a sling, and time. Most heavier injuries also do well without surgery, although a visible bump on top of the shoulder may remain.
Some people develop ongoing pain at the AC joint long after the initial injury has settled, often from wear and tear in the joint surfaces. This usually responds to physiotherapy, painkillers, or an injection. Surgery is only considered if pain continues for months despite these measures.
Common causes
- A fall directly onto the point of the shoulder (the most common cause)
- A fall onto an outstretched hand that drives force up into the shoulder
- A direct blow to the shoulder in contact sports such as rugby or hockey
- Bike crashes, especially going over the handlebars
- Heavy impact in rare cases such as road traffic accidents
Who is at risk? Younger people, especially men in their 20s and 30s, are most at risk because they take part in more contact sports and cycling. Anyone who plays rugby, football, mountain bikes, or skis has a higher chance of injuring this joint.
Symptoms
Symptoms vary depending on the severity and duration of the condition. Common symptoms include:
- Pain and tenderness right at the top of the shoulder, where you can press on a small bony bump
- A visible step or bump under the skin in more severe injuries, where the collarbone sits higher than usual
- Swelling and bruising over the top of the shoulder
- Difficulty lifting the arm above shoulder height
- Pain when reaching across the body (for example, putting on a seatbelt or scratching the opposite shoulder)
- Pain when sleeping on the injured side
When to seek help: Go to A&E or see your GP soon after a significant shoulder injury, especially if there is a visible bump or deformity. An X-ray is needed to check the bones are not broken and to grade the injury.
How is it diagnosed?
Your surgeon will take a detailed history and examine the joint. The following investigations may be arranged to confirm the diagnosis:
- Clinical examination, looking for tenderness, a visible step, and pain when reaching across the body
- X-ray of both shoulders for comparison, which shows how much the joint has separated
- A special X-ray view of the AC joint, which gives a clearer picture of the joint
- Occasionally, an X-ray taken while holding weights, to see how unstable the joint is
X-rays of both shoulders on the same film are useful, because they let your doctor compare the injured side with the normal one. An MRI or ultrasound is rarely needed for this injury.
Treatment pathway
Treatment is tailored to the severity of the condition, your age, activity level, and overall health. Most conditions are treated in a stepwise fashion, starting with the least invasive options.
Sling and pain relief
A broad arm sling for comfort, usually worn for 1 to 3 weeks. Simple painkillers as needed. Most people return to gentle activity within a few weeks.
Sling and physiotherapy
Even when the joint is clearly separated and there is a visible bump, most people do well with a sling for a few weeks followed by physiotherapy. The bump may remain but the shoulder usually works well.
Surgery to repair or reconstruct the joint
Surgery is offered for the most severe injuries where the joint is grossly displaced, or for people who have ongoing pain or weakness many months after a moderate injury that did not settle with non-surgical treatment. Surgery uses a combination of strong stitches, button devices, or grafts to hold the bones in the right position while the ligaments heal.
Recovery
Most people recover well without surgery. Pain settles quickly over the first few weeks, and shoulder movement returns over the following months. A visible bump on top of the shoulder is normal and does not usually affect function. Even people who go on to need surgery later usually do well in the end.
- Mild injuries, return to normal activity: 4-8 weeks
- Moderate injuries, full recovery: 6-12 weeks
- Return to contact sport: 2-4 months
- Recovery after surgery: 4-6 months
What results can I expect?
Mild and moderate injuries have an excellent outlook, with most people returning to full activity including sport. The main long-term issue is the cosmetic bump on top of the shoulder, which surgery does not always fully correct.
AC joint injury - what to expect
Common activity questions for this condition. Timelines are approximate, always follow the specific guidance given by your surgeon and physiotherapist.
| Activity | Typical timeline | Notes |
|---|---|---|
| Drive | Weeks 4–6 | Types I–II: when sling is off and comfortable. Types III+ with surgery: 6–8 weeks. |
| Return to desk work | Weeks 2–4 | When sling allows typing. Types I–II: often within 2 weeks. |
| Non-contact sport | Weeks 4–8 | Types I–II return quickly. Types III with surgery: 8–12 weeks. |
| Contact sport | Months 1–5 | Types I–II: 4–8 weeks. Surgical stabilisation: 4–6 months after confirmed healing. |
| Swimming | Weeks 4–8 | Once wound healed (if surgery) and shoulder comfortable. |
| Overhead lifting | Weeks 6–12 | AC joint can remain tender with overhead loading for several months. |
Common concerns during recovery, and whether they are expected.
Your questions, answered
Plain-English answers to the things people most often ask, drawn from real patient questions and grounded in published guidance. Tap a question to open it.
About thisWhat is an AC joint injury?
The AC (acromioclavicular) joint is where the collarbone meets the tip of the shoulder blade. A fall onto the shoulder or a contact-sport knock can sprain or tear the ligaments there. Injuries are graded from a mild sprain to a full separation.
Your choiceDo I need surgery?
Most AC joint injuries are managed without surgery: a sling for comfort, pain relief and a guided return to movement. Surgery is usually reserved for the most severe separations or for symptoms that do not settle. Even some higher-grade injuries do well without an operation, so it is worth a specialist discussion.
Pain & sleepHow do I manage pain and sleep early on?
Simple pain relief such as paracetamol (and an anti-inflammatory if suitable for you), a sling for the first days to weeks, ice, and sleeping propped up all help. Start gentle hand, wrist and elbow movement straight away, and come out of the sling as comfort allows to avoid stiffness.
The bumpWill the bump on my shoulder go away?
If a step or bump remains, it is the end of the collarbone sitting higher than the shoulder blade. It often stays even after the pain settles, but for most people it is a cosmetic issue rather than one that limits the shoulder. Raise it with your surgeon if it bothers you.
Getting backHow long until I recover?
Many people settle over roughly 6 to 12 weeks, with movement returning first and strength later. Return to contact sport is usually a bit later and is guided by your strength, comfort and confidence rather than a fixed date.
UrgentWhen should I seek urgent help?
Seek urgent review if the skin over the bone looks stretched and about to break, if there is severe deformity, or if the hand becomes numb, cold or pale. After any major chest or shoulder trauma with breathing difficulty, treat it as an emergency.
WellbeingIs it normal to worry about how my shoulder looks?
Yes. A residual bump can be frustrating, especially if you are active. Most people function well and adapt to it; if the appearance or ongoing symptoms trouble you, that is a reasonable thing to discuss with your surgeon.
- NHS: Shoulder pain
- NICE CKS: Shoulder pain (clinical knowledge summary)
- British Elbow & Shoulder Society: Early exercises for shoulder problems and sling care
- British Elbow & Shoulder Society: Patient information
These links are to UK clinical guidance and patient information from recognised organisations. This page is for general information and does not replace personalised advice from your own clinical team.
Preparing for surgery?
Read our step-by-step guide - what to expect before, during, and after your procedure.
How is it diagnosed?
- ✓Clinical examination, looking for tenderness, a visible step, and pain when reaching across the body
- ✓X-ray of both shoulders for comparison, which shows how much the joint has separated
- ✓A special X-ray view of the AC joint, which gives a clearer picture of the joint
- ✓Occasionally, an X-ray taken while holding weights, to see how unstable the joint is
Recovery milestones
- ●Mild injuries, return to normal activity: 4-8 weeks
- ●Moderate injuries, full recovery: 6-12 weeks
- ●Return to contact sport: 2-4 months
- ●Recovery after surgery: 4-6 months