Big Paws Only Dog Forums

I just got a Saint puppy with poor conformation behind. He is 13 weeks old and was kept in a confined area until he came to our house. If he was a horse I would say that he is cow hocked. The question is, is it POSSIBLE that it is a growth and/or strength issue (he is a bit underweight, but eating VERY well) and he will straighten out as he gets stronger or is it just poor breeding?? Opinions please? He goes to my vet on Saturday for a general check up.

Thanks for your help.