Obesity is a risk factor for OA. It causes increased force across weight-bearing joints, which can contribute to cartilage breakdown and, therefore, to OA. As compared to non-obese people, obese individuals are more likely to develop OA in both knees or in both hips rather than in just one knee or one hip.
Interestingly, obesity increases this risk not only for weight-bearing joints such as the knees and hips, but also for non-weight-bearing joints such as the hands. Scientists aren't sure how obesity contributes to OA of the hands, but studies have shown that obese individuals are more likely to develop it.
Body mass index (BMI) is a popular way of evaluating obesity. Your BMI is calculated using a simple formula that takes into account your height in centimeters and your weight in kilograms. Values of about 18.5 to 25 are considered normal; higher numbers indicate overweight or obesity. Having a body mass index in the range of 30-35 increases your risk of developing OA of the knee by four to five times.
If you are overweight, losing weight may help to slow the progression of OA, especially in weight-bearing joints. In addition, weight loss may postpone the need for hip or knee joint replacement. If such surgery is needed, it is likely to have fewer complications in people who are not overweight.