Fastdogz,
I know it's not exactly an answer to your question but.....
Do you have one of those Doggy hydro pools anywhere near you?
I know it sounds a bit poncy, but if your dog does not mind water this can really help!
It's not a miracle cure, but it's a way of excercising without putting any strain on the joint's or muscles......and in the process can strengthen them.
It's never going to cure him back to his old running days, but may help so he will be able to have a bound along the beach or chace that bit of toast!!!
Just a suggestion