Has he been checked for the genetic disorder Osteogenesis Imperfecta? This can cause bow leggedness in babies and kids.  I would get this checked out!!! I know I have OI and even though I didn't have this I have several friends who did.

Get it check out, I hope this helps,

Brianna

I don't know anything about premature babies except the lung and digestive problems that they can have, but I would absolutely get his vitamin D level checked as this could possibly be RICKETS.  It's a bone development disorder that has been known since 1822, and the primary and very visible symptom is bowed legs.  There's tons of info on vitamin D on my profile with one paragraph about rickets.  Let me know if you have any questions.  Take care.  Larissa