Have hot red knee. It is not swollen. For the past four months my left knee has been bothering me. It hurts when I go up and downstairs and when I walk. It even feels weird like it's popping sometimes (like when you crack your knuckles). I was trying to figure out if it was localized. When it hurts it's sometimes on top, sometimes on the bottom - when it feels weird and kind of pops, it's in the back. I used to play tennis and volleyball, but I don't anymore. I don't really excercise but I walk everywhere.