My regular vet is a reproductive specialist for the most part but great for regular vet care. He was not sure what was going on with Spirit after x-rays and a flexion test so suggested stall rest, glucosamine, chondroitin sulfate, bute and MSM.
We did that but haven't seen much improvement.
Had another vet out that works with lamenesses today and she checked all his hooves, did flexion on all legs and said it looks more like hock/hip/stifle than his crooked hoof. She didn't have a definitive answer either but feels it is probably arthritis or possibly some kind of fibro-something or other where they build up scar tissue in the muscles/tendons above the hock. Either way, he is barely lame and she feels we can start using him again and see how it goes, just easy trail riding, no big hills or galloping much. We're going to put him on Cosequin and keep up the MSM. He is so fat right now from lack of work and turn-out!! So, he's serviceably sound