Arthritis Research UK published a report in 2009 entitled “Osteoarthritis and obesity” in which they highlight the severe consequences of obesity for musculoskeletal health. Throughout the report, however, the mechanical effect of excess body weight is assumed to be the direct cause of osteoarthritis (OA). Although this assumption is common, is it supported by the evidence? A survey of the studies associating OA with obesity is inconclusive on whether body weight is the causative factor. The increase in direct-loading on joints due to weight-gain is not as great as is often believed, and compensatory gait patterns ameliorate much of the kinematic effects. One manifestation of obesity, however, is increased adipose tissue—a rich source of proinflammatory endocrine factors. I propose that body weight might not be the main problem in OA pathogenesis, but that increased adipose tissue itself might be both an indicator and a driver of widespread disease.