I have not gone through this, but I can see where you'd be really concerned. I'm a little surprised your vet didn't want to investigate a possible injury further. I would want xrays to see if anything could be found. If he is compensating for some kind of injury, the problem w/ waiting is that 1) it might not ever heal properly and 2) his new, compensating gait could become permanent and/or result in constrictions, or strange muscle development etcetera. Did the vet palpate his legs all over? And test his range of mobility? If it truly has nothing to do with anything physical, then you'd have to start exploring neurological issues.
I don't really have any answers for you, but I sure hope this resolves quickly for your baby - I hope it is nothing. Keep us updated.
