Some joints in the body are more likely to develop problems from normal wear and tear. Degeneration causes the cartilage that cushions the joint to wear out. This type of arthritis is called osteoarthritis. Doctors sometimes refer to this type of arthritis as arthrosis.
The acromioclavicular (AC) joint in the shoulder is a common spot for osteoarthritis to develop in middle age. Degeneration of the AC joint can be painful and can cause difficulty using the shoulder for everyday activities.

Causes

We use our shoulder constantly. The resulting strain makes AC joint osteoarthritis a common disorder. The AC joint is under constant stress as the arm is used overhead. Weightlifters and others who repeatedly lift heavy amounts of weight overhead tend to have an increased incidence of the condition, and often at a younger age.

AC joint osteoarthritis may also develop following an injury to the joint, such as an AC joint separation. This injury is fairly common. A separation usually results from falling on the shoulder. The shoulder does heal, mostly without any surgical correction necessary, but many years later degeneration causes the AC joint to become painful.

Symptoms

In its early stages, AC joint osteoarthritis usually causes pain and tenderness in the front of the shoulder around the joint. The pain is often worse when the arm is brought across the chest, since this motion compresses the joint. The pain is vague and may spread to include the shoulder, the front of the chest, and the neck. If the joint has been injured in the past, there may be a bigger bump over the joint on the affected shoulder than on the unaffected shoulder. The joint may also click or snap as it moves called crepitus.

Treatment

Nonsurgical Treatment
Initial treatment for AC joint osteoarthritis usually consists of

• Rest. The first step toward recovery is to avoid activities that cause pain.
• Ice. Apply cold packs for 20 minutes at a time, several times a day, to keep swelling down. Do not apply ice directly to the skin.
• Nonsteroidal anti-inflammatory medicines. Drugs like ibuprofen and naproxen reduce pain and swelling. Like any over the counter medication, please read and follow the label. If you have a history of stomach ulcers, bleeding ulcers or heart conditions, these medications might not be right for you.
• Physical therapy. See below

Nonsurgical Rehabilitation
If you don’t need surgery, range-of-motion exercises should be started as pain eases, followed by a program of strengthening. At first, exercises are done with the arm kept below shoulder level. The program advances to include strength exercises for the rotator cuff and shoulder blade muscles. The goal is to get your shoulder moving smoothly and to learn how to control your symptoms. You will probably progress to a home program within four to six weeks.

Injections may be beneficial for this condition. They may include:

• Cortisone (Corticosteroid)
• Platelet Rich Plasma (PRP)
• Prolotherapy
• Botox
• Trigger Point Injections
• Viscosupplement

Surgical Treatment
If nonsurgical measures fail to relieve your pain, your doctor may recommend surgery.
The most common procedure for AC joint osteoarthritis is resection arthroplasty. A resection arthroplasty involves removing a small portion of the end of the clavicle. This leaves a space between the acromion (the piece of the scapula that meets your shoulder) and the cut end of the clavicle, where the joint used to be. Your surgeon will take care not to remove too much of the end of the clavicle to prevent any damage to the ligaments holding the joint together.

Usually only a small portion is removed, less than one cm. As your body heals, the joint is replaced by scar tissue. Remember, the AC joint doesn’t move much, but it does need to be flexible in order to glide. The scar tissue allows movement but stops the bone ends from rubbing together.

This procedure can be done in two ways. Today, it is more common to do this procedure using the arthroscope. An arthroscope is a slender tool with a tiny TV camera on the end. It lets the surgeon work in the joint through a very small incision. This may result in less damage to the normal tissues surrounding the joint, leading to faster healing and recovery.

The older open method of performing this operation is done by making a small incision, less than two inches long, over the AC joint. The AC joint is very close to the surface of the skin and can be easily reached through a small incision. The surgeon can then use a special saw or other instrument to shave off a small portion of the end of the clavicle. The end result is similar.