Swollen Joints from Workouts?

bekinator

I'm finding that the more active I am on my feet- my faves are biking, running, and soccer- that I get a weird ballish thing on the front-inside of my left knee, and it hurts worse after harder workouts & colder weather. In the past I've had to forfeit workouts alltogether for a period of time for the swelling to go down and the "ball" to disappear.

I hear that this is tendinitis & caused by working out wrong. Has anyone else encountered this problem? What would you suggest to fix it? Any special knee exercises I could do?

I'm right-handed and right-footed so I'm sure I'm doing something to cause this )-: