Purpose: Entire leg strengthening, aerobic conditioning, weight reduction
Start Position: When sitting on the bike seat with the pedal crank in the 6:00 position (down), the knee should be bent approximately 15 degrees.
Action: Rotate legs around pedals 
Parameters: Start with minimal resistance for 5-10 minutes and increase as strength, endurance and joint tolerance improves.  The program below is the goal.

5 Minute Warm Up,  2/10 Resistance,  50-70 RPMs

10 Minutes Moderate Effort, 5/10 Resistance,  50-70 RPMs

10 Minutes Significant Effort

5 Minutes Cool Down, 2/10 Resistance, 50-70 RPMs 

Tips: If the angle is greater than 15 degrees, raise the seat. If the angle is less than 15 degrees, lower the seat. If the range of motion of the knee is insufficient to allow a smooth revolution on the exercise bike then this may not be an appropriate activity