It's pretty large, and it hurts like a bruise when I press on it. When I wear jeans, I can see the bump sticking out. My friend found a bump on the inside of her knee a little while back, and they told her it was a cyst. It was probably from her running track. I run track too, but she said hers hurt a lot and it was hard to run. It doesn't hurt me when running at all. I've been much more "active" with sports lately, between hard volleyball practices and track. Could that be it?