Acromioclavicular (AC) Joint Arthritis


The acromioclavicular (AC) joint is located at the top of the shoulder where the collarbone and highest part of their shoulder blade meet. AC joint arthritis comes in many different forms, but is usually osteoarthritis

The defining thing about osteoarthritis is the breakdown and loss of articular cartilage. In the AC joint, this cartilage covers and protects the ends of the acromion and clavicle bones where they meet each other. As osteoarthritis develops, their cartilage might thin or disappear. While the body might attempt to produce new cells, it isn’t enough to replace the missing cartilage.

Causes of Acromioclavicular Joint Arthritis

Many people who develop AC joint arthritis do so as they age. They often have one or more of the following risk factors:

  • Joint trauma: Serious injury or surgery to the AC joint may not appear for months or even years after the incident.
  • Joint stress and chronic injury: People who spend a lot of time lifting things overhead might experience mini-traumas to their shoulder joints, making them more likely to develop AC arthritis. For example, those who have spent years weightlifting or participating in high-impact sports may be more prone to developing this arthritis.
  • Congenital defect or illness: Metabolic disorders, episodes of gout, or septic arthritis can increase the risk of AC arthritis. Poor bone alignment can also increase the risk of shoulder separations, which increases the likelihood of developing AC arthritis.
  • Age: Cartilage naturally weakens as you age, which is why osteoarthritis is more common in older patients. 

Symptoms of Acromioclavicular Joint Arthritis

Many times, the first symptom people notice is pain and tenderness at the top of their shoulder. They might also have difficulty reaching their arm across their body like when swinging a golf club or putting on a seat belt. In another large portion of patients, they will not have any pain at all. Still, the most common symptoms people with AC arthritis experience are:

  • Pain with certain movements that cause cross-body movement like reaching up and across the body to put on a seat belt.
  • Joint pain and tenderness where the scapula and clavicle meet at the front and top of the shoulder.
  • Pain that radiates into the rest of the shoulder, the base of the neck, or arm. The pain that radiates to the base of the neck could cause headaches.
  • Stiffness and pain after long periods of inactivity.
  • Difficulty sleeping when laying on the affected shoulder.
  • Irritation and swelling of the soft tissue around the shoulder bones.
  • Clicking, popping, snapping, or crunching sensation when stress is put on the joint.

In many cases of AC joint arthritis, the symptoms come and go, but get worse and more frequent as the months and years go on. 

Treatment for Acromioclavicular Joint Arthritis

When the cartilage on the AC joint is gone, it cannot be replaced. So, one of the nonsurgical treatment options that is available is simply modifying your activities. By doing certain activities that aggravate the joint less often or less intensely, it reduces the pain experienced. Applying ice to the area is also used to decrease the pain and inflammation of the joint. Medications like NSAIDs can also decrease the inflammation of the joint, relieving symptoms. 

If these options do not work, a cortisone shot may be recommended. Finally, if none of those treatments adequately reduce a patient’s symptoms, surgery might be considered. However, most patients will never need surgery to address their AC joint arthritis. The surgical procedure will remove tissue fragments or reshape the bones in the joint to help reduce friction and promote pain-free range of motion. Sometimes the surgery is actually a removal of a portion of the collarbone. The AC joint is unique in that it is one of the few joints that you can live without a portion of the bone. The procedure is often an arthroscopic procedure, using only a small incision. 

Acromioclavicular Joint Arthritis at OAR

People experiencing chronic shoulder discomfort or pain should not ignore their symptoms. Getting treatment for the condition can encourage healthy functioning of the joint and can help minimize or even halt symptoms from progressing. The team at OAR are here to accurately diagnose AC joint arthritis and recommend proper treatment.