I found out about this stuff from a local pet supply store about 7 years ago. It was recommended for our old guy who had become grumpy and less interested in playing in his old age. After awhile of taking it, he became like a puppy again. It blew us away how well it worked! He wasn't grumpy and was full of energy again.
Now, we have another old one, about 110 lbs., came to us with a bum hip and not much muscle left. We started to give this to her and now she can move better and is able to go on...