When my vet was last here I was telling her my oldie was getting intermittent lament and she said she’d seen great improvements with this supplement in many horses.
The stuff that is banned tends to work... devil's claw and meadowsweet, and also boswellia as well. Most buteless/no-bute supplements contain some mix of these.
Regarding joint supps, the main things is making sure they actually contain proven amounts of each supplement. For a 500kg horse, 10,000 mg glucosamine HCl, 5000 mg chondroitin sulphate, 100mg hyaluronic acid, 10,000-20,000mg MSM, 12,500 mg green-lipped mussel, etc...
I used the equine answers bute free version for my arthritic horse. It is banned as its liquid devils claw and we do dressage, but it does help I think so just don’t use it for 48 hrs before a show because that’s the withdrawal advice. In my mind it just keeps him loose for training and everyday
I also had bozmerix which is Boswelia after his hock injections but it was £300- and I am not sure if the impact came from the injections, the cartrophen or the bozmerix but the combination of all of them helped him so much he became sound after being slightly unlevel for 2 months. I finished bozmerix about 2 months ago, and he is still sound off of that with the equine answers bute free. I am only giving the devils claw because I bought a big can of it and had it anyway. The cost of bozmerix and the fact he is still sound having not had it for 2 months makes me think I wouldn’t bother with it next time round