M.B.
I had hip dysplasia at birth, and so did one of girlfriend's kids. Both treatments were the same, which were braces to wear until socket closes enough to keep the joint from separating. Was he breech? I think that is the most common reason for the socket not to close enough. To be honest, I forget most of the info, but if you google it I am sure you'll find lots of info!
By the way, I have had no problems with my hips at all since I was a baby, and my friend's daughter is 9 and she is also fine! Good luck at the doctor! :)