Baily has LP and has had it since he was 4 months old. I got him from a BYB (although I didn't know it at the time). Anyway, I put him on Synovi granuals and ever since then he hasn't had a problem with his joints popping out (knock on wood). It's basically the Glucosamine in the Synovi that helps so much but I use the Synovi because it has other Vitamins that are good for him. I'm not sure if this would completely correct your baby's problem but it might help.
