Your acromioclavicular (AC) joint is at the top of your shoulder where your collarbone and acromion part of the shoulder blade meet. If you have AC joint arthritis, the top of your shoulder might feel painful and you may have problems reaching your arm across your body. There are different types of AC joint arthritis but the most common is osteoarthritis.
What is osteoarthritis?
Osteoarthritis – or wear and tear arthritis – is linked to ageing and it can affect any joint in the body. It is more common in men, especially those who do manual overhead work or sports. Over time, people with AC joint arthritis experience a loss of articular cartilage, which is the flexible cushioning tissue that covers the ends of the acromion and clavicle bones, allowing them to slide smoothly over each other as you move your joint. As the cartilage thins, the bones may start to rub together causing small fractures and thickening of the bone.
Symptoms of AC joint arthritis
Pain from AC joint arthritis is less common than the pain caused by arthritis in weight-bearing joints, such as the hips and knees. However, you may struggle with cross-body movements, such as reaching to put on a seatbelt. You may also experience pain when you reach over your head or behind your back.
AC joint arthritis can cause the growth of bony spurs which may pinch the rotator cuff muscles and tendons that run below. When this occurs the pain is often felt over the upper arm rather than the shoulder and mimics a condition called shoulder impingement syndrome.
Who is at risk?
Most cases are in men who have done a lot of overhead work or activity. It may also affect people with other types of joint problems such as rheumatoid arthritis. Sometimes AC joint arthritis develops after an historic injury to the joint such as a shoulder separation or dislocation.
It is important to see a doctor if you are experiencing symptoms that may be due to arthritis as an early diagnosis may help you avoid activities that are contributing to the condition. During a physical examination, your doctor may perform a cross-body adduction test, which involves moving your extended arm across your body to assess any pain in the top part of your shoulder. You may be given other diagnostic tests, including injecting local anaesthetic into the affected joint to pinpoint the location of any pain, X-rays which can reveal bony spurs or an MRI scan to check if the bone and joint is inflammed.
If you are diagnosed with AC joint arthritis you should minimise movements or activities that cause pain, such as weightlifting or overhead weak. A warm compress can help to ease stiffness and a cold compress after exercise may be effective at decreasing swelling. A physiotherapist will be able to recommend exercises to stretch and strengthen the surrounding muscles to maintain movement in the shoulder. Painkillers can be effective, but as the condition progresses your doctor may recommend injections of corticosteroids to further reduce swelling and relieve pain.
In rare cases you may need surgery. The most common procedure for AC joint arthritis is resection of the distal clavicle, which involves removing a small section of the end of the clavicle to eliminate friction between the clavicle and scapula. This may not be effective in all cases and your orthopaedic surgeon will discuss the most effective treatment options for your particular condition.
How we help
Orthopaedic surgeons will always tailor-make treatments to the needs of individual patients and will discuss all of the treatment options with you fully so you can reach a shared decision about the best way forward.
If you are experiencing shoulder pain or a loss of function in your shoulder joint, contact us to discuss your diagnosis and treatment options