1. Adjust the height of the bike seat so that your knee is slightly bent when your leg is extended downward. If your knee hurts when the pedal reaches the top, you can raise the seat so that your knee does not bend as much.
2. Start slowly. At first, try to do 5 to 10 minutes of cycling with little to no resistance. Increase your time and resistance bit by bit. The goal is to do 20 to 30 minutes with some effort, and without pain.
3. If you start to have pain, rest or cycle for less time or with less effort.

If you do not have a stationary exercise bike at home, you might find one to ride at your local health club or community center.