Weight and osteoarthritis.

Osteoarthritis is the most common form of arthritis. It increases in prevalence with age. About 5% of the US population is affected with hip or knee osteoarthritis; 9.5% of adults aged > 62 y have knee osteoarthritis. Because of its frequency and associated pain and disability, osteoarthritis accounts for much of the disability in lower extremities in the elderly. More than 70% of total hip and knee replacements are for osteoarthritis. Because osteoarthritis is so common, the modification of factors that increase osteoarthritis risk could prevent substantial pain and disability in the elderly and the use of costly health care services. Overweight persons are at high risk of osteoarthritis in the knee and probably also in the hips and hands. The mechanism by which overweight causes osteoarthritis is poorly understood; a contribution from both local increased force across the joint and systemic factors is likely. Better evidence is needed on the effects of weight loss, but preliminary studies suggest that weight loss can both prevent the onset of symptomatic disease and alleviate symptoms when present.