My 21 year old has arthritis pretty much from head to toe. Poor dear. I have found that if you use the same supplement for years on end they almost get immune to it. So I have mixed it up over the years. All the ones I have tried have worked great... I have used stuff like Cortaflex pellets, fluid flex liquid, and just a general glucosomine (spelling) liquid supplement. The rest have slipped my mind. Pretty much anything with glucosomine in it will do the trick. Once you get them started on it, it is best to keep them on it because they crash if you stop it and they get very stiff.
Hope that helped!