Kiska,
I think this is one question that needs to be asked of your veterinarian. As far as I know, none of us have those qualifications.
I hope you will talk with your vet and have your dog examined thoroughly to find out what the problem is. There are supplements that can help joint and muscular problems. I'm sure your vet will advise you accordingly. And in the meantime, I would limit activity until you can get to the source of the problem. Avoid jumping, running, etc.
Good luck, and take care of that puppy.
Logan

[ July 03, 2001: Message edited by: Logan ]