Osteoarthritis is a progressive joint disease characterized by an imbalance of articular cartilage biosynthesis and degradation attributed to both inflammatory and biomechanical factors. Whereas moderate mechanical loading appears necessary for maintaining healthy cartilage, abnormal joint loading increases the risk of osteoarthritis. Obesity-induced osteoarthritis and the benefits of physical activity may be mediated by systemic levels of proinflammatory mediators as well as local biomechanical factors in the joint.