Everyone has their favorite, and it's true that horses react differently to the various products. The best luck I have had was actually an all-round supplement called ReitSportC; it has high levels of Glucosomine, Chondroitin, and MSM, plus the Biotin complex, probiotics and other "stuff". I've had four horses on it at various times, from a young OTTB gelding with arthritis from a shoulder injury to an aged broodmare with arthritis in her knees and back so bad she could hardly move when I first got her. The improvemnet in all cases was astounding. The gelding was able to go back into work and the mare decided she was bossmare and started kickin' butt and takin' names. They all were able to put on weight easily and maintain it, their feet grew in wonderfully strong, and they literally shone with health. It is pricey at $67 a month through SmartPak (don't know what bulk price is) but it takes real good care of everything. Add a daily wormer and you're done. When $$$ was short I used SmartFlex Senior, again with good success, but it is not as complete nor does it have the joint supp quantity of ReitSport. It runs around $30/mo. You have to give whatever you use a good month to see the result, so it can be a long process of finding the right product. You should notice some difference within two weeks with full effect by the month mark.
I am not one of those who in expressing opinions confines themselves to facts. - Mark Twain
The fact that man knows right from wrong proves his intellectual superiority to other creatures; but the fact that he can do wrong proves his moral inferiority to any creature that cannot. - Mark Twain