Patellofemoral pain syndrome (PFPS) is common source of knee pain while cycling. It generally manifests as a dull achy pain that affects the anterior portion of the knee. PFPS is due to malalignment of the patella (kneecap) on the femur (thigh bone).
On the end of the femur, near the knee joint, there is a groove (femoral groove) where the patella sits. In PFPS the patella does not sit properly in the femoral groove which causes abnormal contact between the femur and the patella. The misalignment can cause excessive wear and tear the cartilage of the backside of the patella or at the femur.
PFPS can be caused by muscle imbalances in the quadricep muscles which can pull the patella outside of its normal position in the femoral groove. Muscle imbalances at the hip can cause poor alignment at the knee joint also contributing to PFPS.
A proper bike fit is key to the prevention of PFPS while riding. Cleat position is crucial to proper knee alignment. If cleats are positioned in a toed-in position in can cause excessive stress at the medial (inside) aspect of the knee. A toed-out position can cause stress at the lateral (outside) aspect of the knee. Saddle height also affects stresses placed on the knee. A low saddle height causes the knee to be excessively bent at the top of the pedal stroke. A saddle that is too high forces the knee to be excessively extended at the bottom of the the pedal stroke.
The first step in treatment of PFPS is to avoid the aggravating activity. If you continue to ride through patellofemoral pain you could cause permanent damage to the cartilage in your knee. Then address your bike fit. Look at cleat and saddle height. Usually once the fit is dialed in knee pain with subside. If you continue to have pain see a physical therapist to address muscle imbalances contributing to your knee pain. If addressed early on PFPS typically responds well to treatment.