So, I'm sitting in my living room with a couple of my kids, and my 9 year old is goofing around on the floor by me. I hear a thump, and he turns to me, while rubbing the back of his head, and says,"Mom, my knee is really hard." I asked him why he was rubbing his head, and he said that it's because he hit himself in the head with his knee. I asked how he managed it, and he proceeded to demonstrate! I couldn't resist taking a picture.