Osteoarthritis (OA) is a disorder involving deterioration of articular cartilage and underlying bone and is associated with symptoms of pain and disability. The incidence of OA in the military increased over the period 2000 to 2012 and was the first or second leading cause of medical separations in this period. Risk factors for OA include older age, black race, genetics, higher body mass index, prior knee injury, and excessive joint loading. Animal studies indicate that moderate exercise can assist in maintaining normal cartilage, and individuals performing moderate levels of exercise show little evidence of OA. There is considerable evidence that among individuals who develop OA, moderate and regular exercise can reduce pain and disability. There is no firm evidence that any particular mode of exercise (e.g., aerobic training, resistance exercise) is more effective than another for reducing OA-related pain and disability, but limited research suggests that exercise should be lifelong and conducted at least three times per week for optimal effects.