AC joint pain and arthritis

What it is

The acromioclavicular (AC) joint is the small joint at the very top of the shoulder, where the collarbone (clavicle) meets the shoulder blade (acromion). Although it is a relatively small joint, it can be a significant source of shoulder pain.

How it usually presents

• Discomfort directly over the top of the shoulder, which you can usually point to with one finger
• Pain reaching right up above shoulder height, particularly at the very end of the movement
• Pain reaching across the body
• Discomfort with lifting overhead, weight training, or sleeping on that shoulder
• Sometimes a visible bump over the joint

Why does it happen?

The AC joint takes load every time you reach overhead or across your body. It wears with age and with heavy overhead or weight training use, and it can also be injured in a fall onto the point of the shoulder. One of the challenges with AC joint pain is that it can mimic several other shoulder conditions: it is sometimes confused with pain arising from the rotator cuff, particularly the subscapularis tendon, and in the early stages it can occasionally resemble a developing frozen shoulder. This is why a careful assessment is so important.

What about a steroid injection?

One of the most useful investigations for AC joint pain is an ultrasound-guided diagnostic injection. By placing a small amount of local anaesthetic directly into the AC joint, we can determine whether this is truly the source of your pain. If the injection significantly relieves your symptoms, it provides valuable information that helps guide future treatment. A small amount of steroid can also be given at the same time to reduce inflammation and provide longer-lasting relief.

How it is assessed

Unlike many other shoulder conditions, scans do not always provide a clear diagnosis. X-rays and MRI scans are often used to exclude other causes of shoulder pain rather than to confirm that the AC joint is responsible for your symptoms. The diagnosis is usually made by combining your history with a careful examination.

Do I need a scan or surgery?

Treatment depends on the severity of your symptoms and how much they affect your daily life. Many patients improve with activity modification, physiotherapy and, where appropriate, an ultrasound-guided injection. If symptoms remain persistent despite these measures, surgery may occasionally be considered, although this is usually reserved for patients who continue to have significant pain despite appropriate non-surgical treatment. My aim is to establish whether the AC joint is truly responsible for your symptoms and, if it is, to help you choose the treatment that is most likely to provide lasting relief.

Treatment options

• Activity modification and physiotherapy
• Ultrasound-guided diagnostic and therapeutic injection into the joint
• Arthroscopic excision of the joint surface where symptoms persist

The shoulder is a complex joint, and several different conditions can produce very similar symptoms. My role is to identify the true source of your pain so that we can choose the most appropriate treatment together.