What is acromioclavicular joint and where is it located?

The acromioclavicular (ACJ) is a small joint between the collarbone (clavicle) and the tip of the shoulder blade (acromion). It is located at the tip of the shoulder forming the highest point of the shoulder. Like many other joints in the body, it has cartilage covering the ends of the bone, is surrounded by a capsule and stabilised by strong ligaments. This joint has minimal mobility. It is involved in overhead arm movement and when the arm is moved across the body.

Arthritis of this joint is more common than that of the shoulder joint (glenohumeral joint) although is less common than that of the hip and the knee joints. It is mostly seen in the middle-aged people and weightlifters and hence the other name of the condition “Weightlifter’s Shoulder”.

What are the symptoms of ACJ arthritis?

Common presenting features include:

• Pain over the top of the shoulder
• Difficulty reaching the arm across the body as while putting on a seat belt or swinging a golf club.
• Pain with overhead movements and when trying to reach behind the back
• Pain after high-intensity activities such as tennis, weightlifting, exercises such as bench press or push up
• Pain when lying of the affected shoulder
• Pain on pressing on the top of the shoulder
• Pain can spread to the rest of the shoulder, neck and front of the chest
• Stiffness associated with inactivity
• Small bump or swelling at the top of shoulder
• Clicking, popping or crunching sensation from the affected joint

What are the causes of ACJ pain?

The common causes include

• ACJ arthritis
• Repetitive strain and chronic injury
• Trauma, sports injuries
• ACJ separation

Problems with this joint are seen in both, young and the aged. In young individuals the joint is involved secondary to injuries/falls or as a consequence of repeated minor injuries due to heavy lifting gym activities. Collision sports such as rugby, throwing sports such as shot put, weightlifting and falls from bike are known to cause ACJ problems.

In older individuals main reason of this joint involvement is arthritis resulting from wear and tear of the cartilage present at the end of the bones. Over time the bones pointed edges called osteophytes can form at the end of the bones. These osteophytes can irritate the neighbouring tendons adding to the pain experienced. The joint space may become narrow or even disappears in advanced stages.

Injuries can cause tearing of the ligaments and disturb the alignment of the bones resulting in joint deformities. This can be quite painful and may require arm immobilization for some time.

How is this ACJ arthritis diagnosed?

The diagnosis can be established clinically on the basis of history and examination findings. Imaging modalities are used in combination with these to confirm the clinical diagnosis. Commonly used modalities include

• X-rays. This may show that the bones are closer together than normal or bone changes such as osteophytes.
• MRI. This can help visualise other tissues such as ligaments, tendons, and muscles in detail. ACJ may show abnormal swelling or excess fluid in or around the joint.
• US scan. This has the advantage of being a quick investigation that can be performed in the clinic and may show changes in the capsule of the joint itself.
• Often an injection of the joint is used to confirm the source of pain as not everyone with arthritic changes has pain.

What are the treatment options for ACJ pain?

Treatment for ACJ arthritis pain requires a multimodal approach using a combination of activity modification, physical therapy, hot or cold compression, medication and injections, if required. Weight lifting, golfing, and exercises involving cross-body arm movement should be avoided. At times only reducing the intensity of the activity may be sufficient rather that giving it up completely.

Simple painkillers like paracetamol, anti-inflammatory drugs and local gels are commonly used for this condition. Anti- inflammatory medications should only be used on clinical advice and for short periods in view of their potential side effects.

Injections. Steroid injections are the most commonly used injections for treatment of moderate to severe ACJ arthritis pain. They can help to confirm the diagnosis and reduce the swelling, pain and stiffness. Using ultrasound guidance helps to improve accuracy, reduce side effects. Some clinicians may also consider PRP (Platelet Rich Plasma) injections although there is not much research regarding their use in this condition.

Surgery may be considered if the symptoms are severe and above modalities fail to provide relief. The most common surgery performed involves resection of a small portion of the end of the collarbone with eventually the scar tissue bridging the gap.

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