Foot Position
In order to check whether your saddle height is correct, place your foot on the pedal with the ball of your foot over the pedal axle and pedal casually. There should be no noticeable movement in your pelvis when your foot passes through the lowest pedal position. If you have to drop your hip in the down stroke, your saddle is too high and must be lowered.
Are you used to pedalling with the middle of your foot or with your heel? Then you have probably been riding with your saddle too low for a long time. If the saddle is too low the body automatically tries to improve the distance between the saddle and pedals by using less of the foot length because the leg must be almost fully extended at the bottom of the down stroke in order to use muscles most efficiently.
Why should you ride with the balls of your feet on the pedals? When you pedal using the balls of your feet the ankle can move side-to-side. This lateral movement is important in order to compensate for the lateral movement of the knee because the knee joint is not simply a hinge.
The knee joint is positioned at a slight angle so that when you bend your legs a slight lateral movement occurs. If the foot position on the pedal does not allow lateral movement in the ankle (as is the case when the middle foot or heel is on the pedal) the knee is forced to minimise its lateral movement. Over time this can lead to knee problems.