Glucosamine is a good start, however there isn't any research done on which single joint supplement helps a dog more so then the other. That is why I prefer to take a multi joint supplement approach. So in addition to Glucosamine I also give Chondroitin, MSM, Bromelain, Boswella Extract, Perna (Green Lipped Mussel) and HA that are all in one supplement. All of those have multiple human studies done to show their effects to help joints and with little researching you can find a ton of information about them.
So yeah, Glucosamine is good, I just prefer to give my pup 7 active ingredients instead of 1. Because who's to say that the Glucosamine isn't what is working for her but it's the HA, or the Perna and etc. You see my point 
And I am kind of a supplement nut, but that's only because labs are known for joint issue, specially when they get older and I have done my homework about them. If anyone wants some of my notes just PM me, I'm a bit slower on this forum as I'm on a lab based forum learning how to teach my girl how to Dock Dive!