I had gotten those "fun" heely shoes, and I was "heelying" down a hill. I got near the bottom, hit a crack in the sidewalk, went head over heels the rest of the way down said hill, and finnally hit the bottom. I had a very strong pain in my right leg, so I walked home and pulled up my pant leg. All the skin on my knee was gone and I still have a scar from the incident.