Try switching his SmartPak supplements to SmartFlex IV. It has more HA and seems to have really worked for my gelding who is 21.
Also, we have been dealing with an ankle soft-tissue injury that’s taken a year to completely heal. Might I also suggest seeing if you have anyone who does MagnaWave in your area – the website is magnawavepemf.com. My boy had three sessions and it really helped him along. Trust me when I say I am skeptical, but after seeing a friend who has racehorses who uses it all the time, I gave it a try.