Ask An Expert: Rheumatoid Arthritis and Degenerative Bone Cysts

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Ask An Expert: Rheumatoid Arthritis and Degenerative Bone Cysts

Question:

Can rheumatoid arthritis cause degenerative bone cysts?

Answer:

Many types of arthritis have been associated with bone cysts, which are round areas of bone that on X-rays look like empty holes (though they are not really empty). Usually the cysts cause no pain or other symptoms, and are just found by chance when someone has an X-ray for some other problem. Frequently, the cause of the bone cyst is unknown. Sometimes, however, bone cysts are associated with other medical conditions, including both osteoarthritis and rheumatoid arthritis, as well as other types of arthritis, tumors and sarcoidosis.

Osteoarthritis, which is sometimes called "wear-and-tear arthritis" or "degenerative arthritis," is characterized by changes in the bones near affected joints. These changes can include loss of cartilage between the bones, as well as the development of bone spurs and bone cysts. You may also see some "whitening" at the ends of the bone, which is called sclerosis.

Rheumatoid arthritis is a very different disease characterized by inflammation of the lining (synovium) of the joints. This inflammation can lead to damage to the bones and other tissues of the joint. On X-ray, you can see loss of the space occupied by the cartilage (Cartilage itself is also not seen on a plain X-ray.) because the cartilage is damaged. There are also changes in the bones themselves, including bony "erosions" (where the bone looks like it has been eaten away), slippage of bones out of normal alignment, and bone cysts.

To make things a little more complicated, patients with damaged joints from rheumatoid arthritis can go on to develop osteoarthritis as well. They may then have all the findings seen with both rheumatoid disease and osteoarthritis. Bone cysts may certainly be seen in these patients.

So in fact, bone cysts can be found both in rheumatoid arthritis and osteoarthritis. Treatment is generally focused on the underlying disorder, not on the cyst itself.

Diana Post, M.D., is an assistant professor of medicine at Harvard Medical School and a member of the Department of Medicine at Brigham and Women's Hospital.

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Last updated:	January 24, 2007