it took me by suprise at first because he didn't tell me (apparently he thought I already knew), and him missing a leg never really crossed my mind. There's no set way to deal with something like that, you just do it because you love them. It's such a non-issue for me that I often forget about it and only when someone else brings it up do I remember that he has a disability.
one of my close relatives is disabled due to a car accident. She has no use of her legs and limited use of her arms. Her parents rely on lots of patience and prayer. And they don't make a big deal out of the little everyday annoyances like most people do.