78 patients with knee osteoarthritis were randomized to aerobic exercise via either treadmill exercise, cycle ergometer exercise, or arm ergometer exercise. In addition to randomized treatment, all patients also performed resistance exercises and stretching exercises for 8 weeks. Outcomes were assessed before and after the 8-week programs. All three groups demonstrated significant improvements over time. Group differences were observed for change in the Timed Up and Go test, pain on a visual analog scale, and the Knee Injury and Osteoarthritis Outcome Score (KOOS) sport/rec scale. Differences were specifically between the treadmill exercise group and the arm ergometer group. Change in the TUG test was significantly greater within the treadmill group compared to the arm ergometer group, while changes in VAS pain and KOOS sport/rec were significantly greater in the arm ergometer group compared to the treadmill group.