At some time, one out of three cyclists suffers serious knee pain (Am J Sports Med, 2010 Dec;38(12):2494-501). It often occurs with a new bike, upon returning to cycling after a long hiatus, or when you are trying to increase either your intensity or your mileage. If your knee starts to hurt while you are on your bike, stop riding and try to find out the cause.
The most common cause of knee pain in bicycle riders is having the seat set so high that it forces you to fully straighten the knee as the pedal reaches its lowest level. You are never supposed to fully straighten your knee when you do any kind of exercise, particularly cycling or running. If you set your seat too low, you will bend your knee excessively and be at high risk for developing pain behind your knee cap. Other common causes of knee pain are over-training, setting your seat too far forward or backward, not having the cleats on your bike shoes set correctly, or not having the correct crank length….