As far as therapy, I know that ultrasound therapy has done wonders for a stallion I know who did something dumb to his hind leg that required surgery, he is now fine and very sound. Another thing that could really help him is the Game-Ready system which uses both compression and cold (cryotherapy) to reduce inflammation. Both of these machines are quite expensive, so probably not an option, but if you know someone with one of them, definitely ask about borrowing because they are both awesome.
Another thing you might want to seriously consider is IM injections of Adequan. There are a few weeks of loading and then you just inject it once monthly and it helps repair the cartilage and has kept a lot of arthritic horse I know perfectly sound in w/t/c and some showing. I have all my horses on this injection, along with monthly IV Legend injections as a preventative, and to treat existing conditions. They are all 100% sound and show succesfully. Just feeding the oral joint supplements has been clinically proven to do bearly anything, even the Corta-RX which is one of the best supplements does very little compared to what the injections will do. You might as well be feeding your horse a 5 dollar bill every time you feed.
Another really great theraputic thing for any horse is cold hosing or icing (cryotherapy) after every time you ride. It reduces inflamation, which makes the horse more comfortable and reduces damage done by riding. Again, all of my horses have "problem" areas iced after they are ridden. For the arthritic ones, usually the front fetlocks and coffin joints, and for the performance horses the hocks, knees and fetlocks. For your guy, I would directly cold hose or ice his bad fetlock. What I have found to work best is the Cryopak sheets(Flexible Ice Blanket/ 0ºC
) polo wrapped on. You're going to want to leave them on for 20 minutes, and it's best if you have a freezer at the barn, but you can also freeze them at home and put them in a well insulated bag and keep it cool at the barn.
Another thing you might discuss with your vet is trying injections of Hylarounic Acid directly into the joint, this is mostly the same stuff as the IV Legend, but it is a lot more effective in spot treatment. He will need to be on stall rest for a few days after the injection, and the risk of infection is higher, but usually you only need to inject every 6 months to a year. I would still do the monthly Adequan with this though.
And just a word about generics, for the IV/IM injections you can get them generically and they are going to work just as well, but for the intra-articular (joint) injection you're going to want the most viscous thing available, which means you're going to be paying mor money for the brand name.
Good luck! And if you have any questions about keeping your horse sound just talk to your vet, or me. I can keep nearly anything sound :P
And just to add: as far as an oral anti-inflammatory goes, you're going to want to stay away from bute for long time use, because it can harm the stomach. And Banamine doesn't act like you want an anti-inflammtory to act in this situation. Your best solution is to crush up Asprin and mix it with hot water into a paste and give it orally about 30 minutes before you ride. Ask your vet about dosage and getting a perscription for it.