Help!! Puppy wont walk, problems with joints.

Hi i was wondering if anyone could give me some advice. I have two 4 week old pups, one pup started walking a few days ago and noticed the 2nd pup was struggling, dragging his legs asif he was showing signs of swimmer syndrome. I have taken him to the vets today to be told there is a problem with his hind hock joints and would be best to put him to sleep. I realy dont want this to happen expecially when the vet didnt do an xray or give me any advice etc. Just wondered if any of you had experienced similar. We have reffered him to a specialist for a 2nd opinion so hopefully something can be done to help the poor chap. He is happy and healthy in himself, eating perfectly and passing urine/stool as normal. Any advice would be greatly appreciated.