Young horse with muscle loss over croup

[4horses]

What would cause muscle atrophy between the point of the hip and the spine (croup area)? The horse’s owner noticed some back pain and told me to stop riding him- that was about 3-4 weeks ago. The horse has been on turnout since. I went out to catch a different horse the other day and he came over to see me.

I noticed he has really lost muscle in that area. I immediately thought about EPM but the muscle loss is symmetrical. I then thought maybe it was nutrition related but he is on the fatter side.

He appears healthy and happy- good energy levels. He’s 5 years old. His owner is aware something isn’t quite right and had the vet out to see him last month- I feel like something is going on as well, but it is nothing I can put my finger on conclusively.

[JB]

PSSM can do this. What breed/breeding is he?

Is the area sore?

EPM often causes asymmetrical muscle loss, but not always.

PPID would be pretty rare at this age, but it’s happened before.

Is this atrophy JUST in the glutes?

Any chance you can post a conformation type pic, and then a close up straight from the side of each foot? A lot of muscle loss causes can be ultimately from hind feet especially not allowing proper use of the hind end.

[IPEsq]

Also make sure it is atrophy and not just the SI becoming more prominent (hunter’s bump).

[Critter]

My 5 yo lost a lot of muscle over his topline when his EDM progressed. I actually hadn’t really noticed it until the vet who hadn’t seen him for a few months remarked…and then it was pretty apparent. I had stopped riding him due to the behavioral stuff (which was happening on the ground and under saddle). He wasn’t really a horse you would have said was neurologic…but then progressed more and more quickly, which is when the muscle changes were more obvious. His was symmetrical…he also had bilateral brainstem degeneration.