Hi there, yes I had and FEI horse for show jumping that suffered from TMJ problems. I had to use a ultrasound before big classes and if it was done properly he was amazing. If I didn't do it or did it quickly he literally would not turn to one side which was terrifyingly dangerous.... The joint can also be injected several times a year.
I've had the chiropractor work on horses with tmj issues and have seen a huge difference!