AC Joint Osteoarthritis – symptoms, diagnosis and treatment

Acromioclavicular (AC) osteoarthritis is the most common type of shoulder osteoarthritis and a well-known culprit of pain in the top of the shoulder. The AC joint is a small joint located between the collarbone (clavicle) and the tip of the shoulder blade (acromion).

Symptoms of AC joint osteoarthritis

Common symptoms of AC joint osteoarthritis are pain in the top of the shoulder that radiates toward the neck and shoulder stiffness. The pain tends to worsen over time but it can also be aggravated with certain activities. It often becomes difficult to perform daily activities that require lifting or reaching your arm across the body (for example, getting dressed, brushing hair and fastening your seat belt).

Other symptoms include:

  • Pain at night and trouble sleeping
  • Swelling
  • Clicking or cracking noises in the shoulder
  • Decreased shoulder motion

If you experience any of these symptoms you should schedule an appointment with a physical therapist or a doctor to get a diagnosis.

Several risk factors play a part

There is no single cause for the development of AC joint osteoarthritis. Several risk factors tend to contribute to the development of the joint disease.  However, manual labor is a main risk factor for AC joint osteoarthritis. Jobs that require a lot of heavy lifting can damage the shoulder over time. 

Heavy lifting and high-impact sports can cause acute trauma to the shoulder (e.g. fractured collarbone, shoulder dislocation, ligament tears) which increases the risk of developing osteoarthritis in the AC joint later on in life. Other common risk factors include age, female sex and obesity.

Diagnosing AC joint osteoarthritis

Traditionally, osteoarthritis was diagnosed by X-ray. Today, it is still a widespread belief that this method is necessary for diagnosis. However, according to the World Health Organization and extensive international research, osteoarthritis should be diagnosed by a healthcare professional through an assessment based on the patient’s medical history, joint function and pain level. The healthcare professional will also take risk factors for osteoarthritis into account and keep them in mind when establishing the diagnosis

Shoulder pain may be caused by osteoarthritis of the glenohumeral joint or shoulder conditions such as subacromial pain syndrome, bursitis, frozen shoulder or rotator cuff disease. Osteoarthritis of the AC joint is therefore sometimes overlooked. If you experience pain or stiffness on the top of the shoulder or shoulder pain that radiates towards the neck, a good first step is to contact your primary healthcare center and schedule an appointment with a physical therapist or a doctor to receive the right diagnosis. 

Occasionally, an MRI examination of the shoulder may be required to rule out other shoulder conditions.

Treating osteoarthritis and shoulder pain

First-line treatment for both AC joint osteoarthritis and many other types of shoulder pain is patient education in combination with individualized shoulder exercises. These individualized exercises should be coordinated by a physical therapist either physically or digitally. Inactivity tends to worsen symptoms.

Shoulder exercises should consistently be adapted to the patient’s abilities based on pain and function level. As a complement to first-line treatment, if the pain becomes unbearable, non-prescription painkillers may be used for short periods of time. You should always discuss the use of painkillers with your doctor to avoid side effects and drug interaction. 

Other treatment methods

If first-line treatment isn’t enough to manage your symptoms, other treatments can be offered in addition to the individualized exercises.  On occasion, cortisone injections are used as a complement to treat severe osteoarthritis of the AC joint. These injections only offer short-term symptom relief and should be administered by an experienced orthopedic specialist. Cortisone injections should be used with caution and only when symptoms are not alleviated by the exercises, as excessive injections may further damage the joint. 

In rare cases, surgery may be necessary. Although surgery can provide good results for many patients, it is never risk-free. All surgery comes with the risk of developing blood clots and infections. The most commonly performed operation for osteoarthritis of the AC joint is distal clavicular excision, which is the removal of part of the collarbone.