Knee Problems?

Bike riding, especially on a stationary bike, can help you stay fit without putting too much strain on your hips, knees, and feet. Adjust the seat height so that your knees maintain a slight bend when the pedal is at its lowest point. Always warm up for at least five minutes. Start slowly, and set the bike at limited or no resistance if you have knee problems. 

Source: Exercise and Your Arthritis, published by The Arthritis Foundation, www.arthritis.org