Posting this for Sam.
We went for a ride yesterday with Rummy and Latte - Sam said Rummy felt 'off' but he wasn't limping so we he4aded out, mostly walking with some tiny amounts of trot. Not a hard workout by any means. We rode up to PC and rode in the arena for a while. Sam jumped off Rummy and just watched me working with Latte.
When she asked him to walk forward, he moved like our old dog who has arthritis and loses her hips - He was wobbly in the back and and didn't seem to have much control. He was also stepping really far under with one leg and very short with the other. He was reluctant to move.
We called our vet who couldn't come out but left us a shot of painkillers at her surgery. We called the big equine vet but they couldn't come out either and were very unhelpful - Saying it had to be tying up or foot soreness.
We don't think it was tying up as he wasn't tense through his rump and his movement was much freer than it would have been - We have had horses tie up before. It was definitely not in his feet, it was up around his hip/pelvis I think.
We got dad to come float us home. He sometimes walked fine, though long with one and short with the other, then the next time he walked off he would do it again.
We got him home, put him in the yard and gave him his shot.
There is no swelling, not heat in either leg. He is bright enough, doesn't seem to be in pain wherever you poke him around his back end.
It seems to me like it might be a pinched nerve or something, but I don't know.
Our vet will be out as soon as she can - But any ideas? We are stumped.