Earlier research has shown that exercising while receiving manual therapy improves function and reduces pain in people with knee osteoarthritis. However, very little is known about the mechanisms by which manual therapy and exercise reduce pain and improve function. This study will ask subjects with knee osteoarthritis to receive one of the following interventions: (1) no treatment, (2) exercise only, or (3) manual therapy only. Measures will be taken of the patient's knee range of motion, knee swelling and pain before and after receiving the intervention. These measures will be analyzed to determine what effect exercise and manual therapy applied to the knee have on improving knee range of motion and reducing knee pain and swelling. Swelling will be measured using an ultrasound device which is used to take pictures inside the knee. This type of ultrasound measurement is painless and harmless.