I am having pain on my knee cap.it increases when i fold my leg.it also increasess when i play football.the pain is on the outer side of the knee cap.

Could be PFTD.: Hard to tell from a short snippet of information, but this could be something called "patellofemoral tracking disorder", otherwise known as "patellar maltracking", wherein the patella does not move across the knee joint as it usually should, which can cause pain from bone-on-bone contact. But, again...could be. An X-ray and MRI of the knee may be helpful.