In rheumatoid arthritis, the body's immune system attacks joint tissues, leading to damage in many parts of the body, including bone, cartilage and various internal organs. The disease can cause severe disabilities, particularly in older people, and its exact causes are still not known.

Women with rheumatoid arthritis whose thigh muscles were strongest also had thigh bones that were more dense, and hence stronger, Dr. Ole Rintek Madsen of Bispebjerg University in Copenhagen, Denmark, and colleagues report in the April issue of the Annals of the Rheumatic Diseases. The findings suggest, they say, that exercise could help preserve bone strength in these patients.

This is of particular interest, Madsen told Reuters Health, because "patients with rheumatoid arthritis suffer a twofold increased risk of osteoporotic fractures due to low bone mass."

Madsen's team investigated the relationship between bone mineral density (BMD) and associated factors in 67 women who had had rheumatoid arthritis for an average of 15 years. Most were or had been receiving treatment with steroid drugs called glucocorticoids, which increases osteoporosis risk.

The strength of the women's thigh muscles, or quadriceps, was linked to several measures of bone strength, independent of age, disease duration and cumulative steroid dosage.

No relationship was seen between quadriceps strength and BMD of the spine and forearm. After adjustment, women who had below-normal thigh bone density were shown to have 20% lower quadriceps strength than those whose thigh bones were of normal density, the report indicates.

This outcome, Madsen explained, "has revealed that reduced muscle strength is a stronger determinant of bone mass than are other traditional markers of disease severity. The finding emphasizes the importance of exercise programs in the prevention of bone loss and osteoporotic fractures in rheumatoid arthritis."

SOURCE: Annals of the Rheumatic Diseases 2002;61:325-329.