Your Guide to AC Joint Pain, Arthritis & Treatment Options

What Is the AC Joint?

The acromioclavicular joint (AC joint) is where your collarbone (clavicle) meets the highest point of your shoulder blade (acromion). This small but important joint allows you to raise your arm overhead, move across your body, and perform many everyday activities.

 

What Is AC Joint Arthritis?

AC joint arthritis occurs when the cartilage that cushions the joint wears out. Without this smooth lining, the bones rub against each other, causing pain, stiffness, and swelling. It is different from glenohumeral arthritis, which affects the main ball-and-socket joint of the shoulder.

Symptoms of AC Joint Arthritis

• Pain and tenderness on top of the shoulder
• Sharp pain when moving the arm across the body
• Discomfort when reaching overhead or lifting
• Pain at night, especially when lying on the affected side
• Reduced shoulder strength or clicking sounds with movement

Causes and Risk Factors

AC joint arthritis often develops gradually through wear and tear, but it can also follow injuries or repetitive use. Contributing factors include:

• Previous shoulder trauma such as fractures or dislocation
• Repetitive overhead activity in jobs (carpenters, painters) or sports (tennis, weightlifting)
• Other shoulder problems like shoulder impingement or rotator cuff tears

People over 40, or those with a history of heavy lifting or shoulder injury, are most at risk.

How Is AC Joint Arthritis Diagnosed?

Your doctor will take a history, perform a physical examination, and order imaging tests if needed:

X-ray

Shows narrowing of the joint space, bone spurs, or changes in the clavicle and acromion.

MRI

Helps detect soft tissue conditions like bursitis, tendon tears, or additional shoulder injuries.

 

Treatment Options for AC Joint Arthritis

Non-Surgical Treatments

Many people improve without surgery. Options include:

• Anti-inflammatory medication (NSAIDs)
• Physiotherapy to strengthen the rotator cuff and shoulder stabilisers
• Activity modification and rest from aggravating movements
• Corticosteroid injections for temporary pain relief

Surgical Treatment

If pain persists despite non-surgical care, surgery may be recommended. The most common procedure is distal clavicle excision, also called the Mumford procedure. This involves removing a small portion of the collarbone to stop painful bone-on-bone contact.

Arthroscopic (Keyhole) Surgery

• Minimally invasive with tiny incisions
• Less than 1 cm of bone is removed
• Usually requires a sling for 1–2 weeks
• Recovery takes about 6–8 weeks

Recovery and Rehabilitation

Recovery after AC joint surgery varies depending on your job and activity level:

• Office or desk workers – return to work in a few days
• Manual labour or heavy lifting – may need 4–6 weeks off
• Sport and gym training – gradual return after 6–8 weeks with physiotherapy guidance

Post-operative physiotherapy helps restore movement, strength, and shoulder function.

Can AC Joint Arthritis Be Prevented?

While not always preventable, you can reduce your risk with these strategies:

• Avoid repetitive heavy overhead lifting when possible
• Use proper technique in sports and gym training
• Strengthen your shoulder muscles and maintain flexibility
• Protect your shoulder from injuries with safe work and exercise habits

When Should You See a Doctor?

If you have ongoing pain on top of your shoulder that limits sleep, work, or sport, it is important to seek medical advice. A GP or shoulder specialist can:

• Confirm the diagnosis with physical tests and imaging
• Discuss treatment options tailored to your lifestyle
• Provide referral for surgical care if required

Helpful Resources

• Orthoanswer – Shoulder Arthritis Information
• Physiotherapy for Shoulder Pain
• Other Shoulder Conditions