Adding again:
IIRC, the worsening of the stifle symptoms, at least under saddle, lines up somewhat with me starting to turn him out in 4 hoof boots.
Add that to the change in balance for me in the saddle, and I think I may have a contributing factor. I’m turning him out in fronts only starting today (which we had no issues with previously, I was just trying to do him a favor with the hind boots ).
We shall see. He was definitely more wonky today than he was not that long ago.