 We are exploring a unique weight-training program for men and women 55 years or older with knee osteoarthritis OA that emphasizes high-speed movements. We believe that the speed at which muscles move may be more important to the improvement of muscle performance, function and pain than how strong the muscles are. We are comparing high-speed power training with traditional strength training to determine which method has the greatest effects on muscle strength, muscle power, speed of movement, functional performance and pain. We believe that high-speed training will improve these measures to a greater extent than simply training for increased muscle strength. 