3 months ago my knee was swollen and had excessive pain, I can't even walk. I happened may be due to excessive walking or exercise. I went to a doctor,  did xray (found nothing) and prescribed some medicine and rest. After few days swollen & pain had gone. But after that "Sometimes"(not continuously) when I bent leg or stand still I feel  mild or can say minor pain in upper side of the knee cap or in sides till now. It's (pain) like comes & goes & no swelling nothing.