Hi, my knee has been painful for quite a while - it gives way, clicks, hurts to bend if ive kept it straight gor about 5mins and when i get up from sitting hurts too. I usually run, however haven t since the pain has got worse. Today however, it seems to have gone purple with darker patches like bruising , althoigh I havent bashed it and it doesnt hurt to touch, just hurts at the top of the knee cap. What could this be?