I'm cool, except for my knees

My nephew, who will be 5 in December, was laying in bed with his mother before bedtime. They were talking about his day, and how several of his friends approached him at school to tell him he was "cool". He proceeded to explain to her WHY he was cool: his spiked hair, his cool clothes, his super cool light up Superman shoes. But, apparently he has one flaw, because he told her: "My knees, however, are HIDEOUS."