Sherlock, if you don't know, is getting old!! We've noticed that he's been having a lot more trouble walking or running for long periods of time. My sister received a sample of this in the mail recently. It comes with a lot of product, which I guess is to give your dog time to react to it so you can determine whether or not it works or not?? I'm not sure haha but I think it certainly is working for Sherlock! :)