SummaryRecreational exercise has achieved great popularity. Possible benefits to participants are increased longevity, decreased risk of cardiovascular disease, improved psychological well-being, and greater fitness. A very important but as yet unanswered concern is whether regular exercise will lead to degenerative joint disease or osteoarthritis. Many factors (e.g. physical characteristics of participants, biomechanical and physical features, nature of the playing surface and sport, manner of participation, preventive measures, and certain medical considerations) might influence the risk of developing osteoarthritis from sports participation. However, none of these have been evaluated. Although studies with animals have identified situations in which articular cartilage degeneration may be accelerated, experimental observations have not found normal joint motion in exercising animals to be harmful to joints. Anecdotal observations in man have suggested relationships between recreational activities and degenerative joint disease. However, those few controlled studies reported indicate that exercise need not be deleterious to joints. We interpret available data as suggesting that reasonable recreational exercise, carried out within limits of comfort, putting joints through normal motions, without underlying joint abnormality, even over many years, need not inevitably lead to joint injury.