There is increasing concern that too much physical activity may lead to osteoarthritis. The continuous stress that physical activity places on the joints can result in microtrauma and degeneration of the articular cartilage. However, the onset of osteoarthritis appears to depend on the frequency, intensity and duration of physical activity. Research has shown that individuals of all ages can tolerate moderate amounts of exercise without adverse consequences or accelerated development of osteoarthritis. However, excessive participation in high impact sports, particularly over a long period of time and at an elite level, can increase the risk of developing osteoarthritis. Participants may also be at risk if they have abnormal joint anatomy or alignment, joint instability, underlying muscle weakness or imbalance, or if they are overweight and engage in significant amounts of exercise. Individuals who have experienced sports injuries to joints, or macrotrauma, may also be at risk of accelerated development of osteoarthritis. Certain types of surgery for the treatment of severe sports injuries, particularly to the knee, also appear to be associated with an increased risk. If surgery to the knee is required, continuous passive motion is an ideal form of rehabilitative treatment, as it promotes healing of the articular cartilage, ligaments and tendons. Moreover, athletes who have undergone surgery should return slowly to sporting activities to ensure they do not place too much stress on their injured joint(s). Further research into the causes of osteoarthritis is required; in particular, prospective and retrospective cohort studies are needed to confirm the association between exposure to risk factors and the development of osteoarthritis.