Previous studies have found that exercise can reduce pain, improve endurance for physical activities, and improve cardiovascular fitness over time. However, these studies have not looked at the impact of exercise programs for older adults with osteoarthritis or at how long older adults continue exercising after a program is finished. This study will look at the long-term effects of a structured exercise program for people aged 60 or older who have osteoarthritis of the hip or knee. One goal of the exercise program is to encourage older people with osteoarthritis to continue exercising.