Why is my German Shepherd limping?

I have a 9 month old GSD. He's really big already, and for the past two months, he starts limping, really badly, on one leg. First, it was on the front, then a week later, that went away and he started limping on the back, I got these vitamins becuase I thought maybe it was a puppy form of displasia, he got better right away, then it started again. It's a different limb everytime, and as soon as one gets better, another one starts. When it hurts him, he's all bummed out and doesn't want to eat. He's still on the vitamins. He gets good excercise, not over doing it, he has a huge down comforter in his kennel, he only goes in there at night and when he wants to in the daytime, he's on really expensive food, which I tried different ones, too. I recently took him to the vet and they took X-rays, she said he doesn't have dysplasia and he doesn't have osteoporosis. She thought maybe the vertebrates looked too close together compared to another dog's, but that was a smaller, completely different breed of dog. She showed the pics to an orthopedic vet friend who now wants more X-rays. Which means more $$$ just to figure out what the problem is and then we have to spend more to fix the problem, if they can find it. I just want my puppy happy. She thinks it may be that he's simply having growing pains from growing too fast. I have him on the correct food, so any suggestions that I may be able to research would be very welcome, or maybe someone else has had a similar problem. Thanks.

that's happened with my german shepard. his was from both walking to much and he stepping on little sharp things mainley outside. so I put some flour on it...yes baking flour (hahaha) and he was better the next day. flour also helps if he's bleeding!

Sounds like a very common problem in large-boned young dogs. Do you have him on a food that is labeled for large breed puppies? You should. In the meantime, this shouldn't be a mystery to a good vet - and you should be asking your dog's breeder if they are reputable. Read this:http://www.lowchensaustralia.com/health/pano.htm Ask for a low dose of Rimadyl, and only give it to him if he is obviously in pain that bothers him. You may also want to put him on some fish oil capsules and a little powdered giner, both of which are excellent anti-inflammatories.

he could have a fractured or broken bone take him to the vet

probably because hes a very athletic dog like most german Shepard'ss. my dog did the same thing. rest his legs and keep him active like walks but no running.