Does excess weight cause osteoarthritis and, if so, why?

Osteoarthritis is a slowly evolving degenerative disease affecting cartilage and bone. Like other chronic non-infectious diseases, its aetiology appears to be multifactorial and therefore preventable by risk factor modification. One ofthe best studied potentially modifiable risk factors is obesity. While this review will use the concepts of adiposity and weight interchangeably, it should be recognised that these are biologically different phenomena, one representing an increase in adipose tissue and the other representing increased force across weight bearing joints. Risk factors for osteoarthritis are different, depending on which joint is affected.' Knee injuries, like those sustained in football, predispose to knee osteoarthritis but obviously not to hand osteoarthritis. Some factors may have purely local effects, whereas others have systemic effects. The effects of weight (or adiposity) may be both local and systemic.