Once when i was a kid i slipped while running down the driveway and scraped my knee so bad that the kneecap was exposed. That was about twenty years ago but i still have a big circular scar. It fells all squishy when i put my finger on it. I remembver quite clearly that it didn't hurt until i looked at it. Not as severe as some of the ones on here but it seemed pretty fucked up to me at the time.