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AC Joint Arthritis
What Is Acromioclavicular Arthritis (AC Joint Arthritis)?
Pain and tenderness at the top of the shoulder and difficulty reaching the arm across the body—to swing a golf club or put on a seat belt, for example—may be a sign of acromioclavicular arthritis. The acromioclavicular (ah-kro-mee-o-klah-vik-u-ler) joint, also called the AC joint, is located at the top of the shoulder where the clavicle (collarbone) and highest part of the scapula (shoulder blade) meet. Most people are not familiar with this joint in the body, but arthritis in the AC joint is actually more common than arthritis in the glenohumeral joint, the shoulder’s large ball-and-socket joint. Typically, arthritis is indicated by a gradual onset of pain, tenderness and limited range of motion. Acromioclavicular arthritis comes in many forms, most commonly osteoarthritis.
AC Joint Osteoarthritis and Cartilage Loss
The defining feature of osteoarthritis is the breakdown and loss of articular cartilage. In the AC joint, slippery, flexible articular cartilage covers and protects the ends of the acromion and clavicle bones where they meet.
During the development of osteoarthritis, cartilage may thin or disappear. The body may attempt to produce new cells, but it is not enough to replace the missing cartilage.
AC Joint Osteoarthritis and Shoulder Pain
- Bone marrow lesions. The bone underneath the damaged or missing AC joint cartilage may develop areas of abnormal swelling called bone marrow lesions. These lesions seem to be associated with pain.
- Minor shoulder dislocation. If the acromion is positioned just a few millimeters out of place, termed AC subluxation, it may indicate the shoulder pain is coming from AC joint arthritis. A minor dislocation will not necessarily be obvious to the patient or even the doctor without an x-ray or other medical imaging. AC joint arthritis can also occur after a complete dislocation.
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How is arthritis of the AC joint treated?
When the cartilage is gone from the joint, there is no way to replace it. As a result, one way to treat arthritis is to modify your activities so as to not aggravate the condition. This does not mean giving up activities entirely but it may mean doing certain ones less often or with less intensity. For example, weight lifters may bench press only three quarters of the way down instead of doing a full bench press — or to exercise their pectoralis muscle (muscle made stronger by bench press), they may do a lift called a butterfly, which does not seem to irritate the joint as much as bench press.
Other ways to treat arthritis of the AC joint include the use of ice and medication. Application of ice to the joint decreases the pain and the inflammation at the joint. It is recommended that the more the joint hurts the more ice be used. Ice should be particularly applied after athletic activities — or if the joint is very sore, ice should be applied daily or as often as every two hours. Ice should be applied for 20 to 30 minutes directly to the joint either using an ice bag or by massaging the joint with ice cubes. Since the joint is relatively small, ice massage can be very effective, and paper cups filled with water and placed in the freezer make great ice cones for massaging the joint.
Medication that can typically decrease the inflammation includes aspirin or medications called nonsteroidal anti-inflammatory drugs. These are medications like aspirin but do not have to be taken as frequently as aspirin and include ibuprofen (Advil or Motrin), naprosyn (Aleve), Feldene, Clinoril, Daypro, Indocin and others.
What can be done if those treatments do not work?
When the cartilage is gone from the joint, there is no way to replace it. As a result, one way to treat arthritis is to modify your activities so as to not aggravate the condition. This does not mean giving up activities entirely but it may mean doing certain ones less often or with less intensity. For example, weight lifters may bench press only three quarters of the way down instead of doing a full bench press — or to exercise their pectoralis muscle (muscle made stronger by bench press), they may do a lift called a butterfly, which does not seem to irritate the joint as much as bench press.
Other ways to treat arthritis of the AC joint include the use of ice and medication. Application of ice to the joint decreases the pain and the inflammation at the joint. It is recommended that the more the joint hurts the more ice be used. Ice should be particularly applied after athletic activities — or if the joint is very sore, ice should be applied daily or as often as every two hours. Ice should be applied for 20 to 30 minutes directly to the joint either using an ice bag or by massaging the joint with ice cubes. Since the joint is relatively small, ice massage can be very effective, and paper cups filled with water and placed in the freezer make great ice cones for massaging the joint.
Medication that can typically decrease the inflammation includes aspirin or medications called nonsteroidal anti-inflammatory drugs. These are medications like aspirin but do not have to be taken as frequently as aspirin and include ibuprofen (Advil or Motrin), naprosyn (Aleve), Feldene, Clinoril, Daypro, Indocin and others.