The naughty left knee

Last Thursday I've noticed my left kneww was swollen quite a bit. It felt warm, however I did not feel any pain.
I couldn't decide what could have caused this. I've run 8km the eve before but - that is not much at all. Anyway I took some diclofenac before going to work and later, in the evening I've applied some ice to it, raised it during the night and had some more diclofenac.

No sign of getting better Friday, but then I could feel some very mild pain on the outer side of the knee. I've searched the internet for the anatomy and any probable causes and finally decided: I had a lateral collateral ligament injury. What could do that to me? I'm still uncertain & puzzled.
Anyway, I kept on icing and raising it while eating more and more diclofenac. By now it is not swollen anymore, only a very light breeze of pain remains if I push the ligament hard.

Question is: should I enter the upcoming Tour de Tisza-tó? 55 km of skating on the 9th of May. Hmmm hmmm hmmmmmmmm

BTW did you know that European rivers are all polluted with diclofenac? It seems to be the most commonly used drug here nowdays...