Obesity and osteoarthritis of the knee in women: results from the Matsudai Knee Osteoarthritis survey

A 14-year longitudinal study of middle-aged women was conducted to evaluate the role of obesity in the initiation and progression of idiopathic knee osteoarthritis and to investigate the effect of weight loss on its natural course. Of the 1191 women participating in the first Matsudai Knee Osteoarthritis Survey in 1979, 608 women without possible secondary osteoarthritis were re-evaluated in 1993. Data were collected by questionnaire, physical examination, and weight-bearing anteroposterior knee radiographs. The mean age of the subjects was 51.3 (range 40–65) years with mean body mass index (BMI) of 23.0 (range 16.0–34.7) at the first survey. Incident disease was defined if a grade 0 knee (a modified Kellgren and Lawrence scale) at the first survey advanced to grade 2 or higher at follow-up. Progression of the disease was defined if a grade 1 or 2 knee advanced to a higher grade at follow-up. We found that higher BMI at the first survey increased the risk of both the initiation and progression of knee osteoarthritis. Obese women (BMI≧25.0) with a decrease in body mass index of 2 units or more during the 14 years had a lower risk for radiological deterioration, although weight gain did not alter the risk significantly.