Hello. I have a small lump the size of a pea under my knee cap, and when i walk it come out to the size and hurts, i can move it by touch, put it back under the cap, but then as soon as i walk it pops back out again, sometimes even on the other side of the knee. I cant walk as it is very painful but i do not know if it is the ball that is causing pain or a pulled muscle from training. All i know is when i press the ball, it does feel very uncomfortable, but not a sting, more of a heavy ache. thanks