swollen knee

Did a long tempo on Thursday...felt great no pain what so ever. Woke up Friday morning with a swollen left knee. Figured it was because I havent been rolling as often as I should...now it's Sunday, I've been rolling it out a couple times a day, and it is still a little swollen. Any ideas?

I gave it a little 1/4 mile run yesterday to see if it hurt running, and there is absolutely no pain.