Acupuncture,my FRiend, acupuncture. It worked wonders on our English Shepherd with a messed up back from prior abuse. We're using it now for our 9 y.o. Aussie mix with a bad hip and knee and he can play like a puppy with our pointer-setter mix and go for long walks.
If you're concerned about his weight, try the green bean diet. Slowly substitute cooked green beans for half his kibble, so he feels full without the calories. We buy frozen green beans and cook 'em ourselves, rather than buy the canned green beans because of all the salt. Of course, we warm the greens up with a little canned dog food to make them mare palatable, not that our dogs are spoiled....
Do you perform the acupuncture yourself or see a vet/tech for it? Have you discussed the gb diet with your vet, and if so the feedback you received?