About two days after that, I rode him again. This time, he had shoes on all four feet, and they were secure. But, he hasn't had shoes on his back feet since he retired from the track 3-4 years ago. They were also slightly too big for him, and stuck out a bit on his heels. He would walk, stop, turn, and back up, but that's it. He would not move into a trot. Every time I nudged him, kicked him, or clicked to him, he stopped, and wouldn't move. The only thing that had changed since I'd rode him the first time were his shoes, him having new ones put on, and shoes were put on his hind feet for the first time in about 3 or 4 years.
Does anyone know what could possibly be wrong with him? Is there anything that I need to be concerned about?