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* Objective: To evaluate the effect of weight loss in preventing symptomatic knee osteoarthritis in women. * Design: Cohort analytic study. * Setting: The Framingham Study, based on a sample of a defined population. * Patients: Women who participated in the Framingham Knee Osteoarthritis Study (1983 to 1985): Sixty-four out of 796 women studied had recent-onset symptomatic confirmed osteoarthritis (knee symptoms plus radiographically confirmed osteoarthritis) were compared with women without disease. * Measurements: Recalled date of symptom onset was used as the incident date of disease. Historical weight was defined as baseline body mass index up to 12 years before symptom onset. Change in body mass index was assessed at several intervals before the current examination. Odds ratios assessing the association between weight change and knee osteoarthritis were adjusted for age, baseline body mass index, history of previous knee injury, habitual physical activity level, occupational physical labor, smoking status, and attained education. * Results: Weight change significantly affected the risk for the development of knee osteoarthritis. For example, a decrease in body mass index of 2 units or more (weight loss, approximately 5.1 kg) over the 10 years before the current examination decreased the odds for developing osteoarthritis by over 50% (odds ratio, 0.46; 95% Cl, 0.24 to 0.86; P = 0.02). Among those women with a high risk for osteoarthritis due to elevated baseline body mass index ([is greater than or equal to] 25), weight loss also decreased the risk (for 2 units of body mass index, odds ratio, 0.41; P = 0.02). Weight gain was associated with a slightly increased risk for osteoarthritis, which was not statistically significant. * Conclusion: Weight loss reduces the risk for symptomatic knee osteoarthritis in women.

Osteoarthritis is characterized by joint pain and inflammation, cartilage breakdown, and the formation of fibrous tissue and cysts on bones. It is the most common condition affecting the joints. The knee is the joint that is most frequently involved, resulting in reduced ability to walk. People with osteoarthritis visit their doctor twice as often and have more days of restricted mobility than people without this condition. Once osteoarthritis develops there is not much that can be done to alter the course of the disease. Estrogen therapy is used in postmenopausal women to protect against bone loss. Some have proposed that estrogen may increase bone mass and stiffness, and lead to cartilage damage and osteoarthritis. Previous studies have suggested that estrogen may be involved in the development of osteoarthritis in women. Since estrogen therapy is common in postmenopausal women, it is important to determine the relation between estrogen therapy and osteoarthritis. A group of 831 postmenopausal women, with an average age of 73 years, were evaluated for osteoarthritis of the knee. The women were divided into groups based on the amount and length of time of estrogen use. Radiography analysis of the knees showed no relation between estrogen use and osteoarthritis. In some cases a protective effect of estrogen was indicated, but the effect was not statistically significant. These findings demonstrate that estrogen does not increase the risk of developing osteoarthritis. (Consumer Summary produced by Reliance Medical Information, Inc.)