I recently visited a family to drop of a PC. On entering the living room I sat down and 6-7 year old son approached "Mum why is that man walking like that"?

There was the usual mumbled "shhh - mustn't say..." etc & I interrupted "S'ok" and I proceeded to briefly explain using two fingers to show differing leg sizes how both knees bend in order to allow my feet to reach the floor and so I walk funny. It works most of the time :)

It was many years before I came up with this as a quick and simple explanation - I used to get embarassed and move away when I was younger or scowl / growl at children who were really just being curious.

What do you do say ??