Guessing Games are fun!

So I have this magnificent bruise on the outside of my left thigh down by the kneecap. It's about six inches long and three inches wide and it's all deep purple and black. It's going to turn an outrageous shade of green as it heals, I can tell.

So lets play a game, kay?  How did Katie come by such a wondrous battle wound?

C'mon guess!