So...not long after he got shipped down to Georgia from Maryland last year, for a while (August) my horse was kind of...sliding his hind feet as he walked. He'd set his foot down, it would slide forward a few inches, he'd pick it up...and so on. The vet saw it when she was out for something unrelated and though she thought it was odd and unusual, she didn't seem particularly concerned.
Over time, it went away so I chalked it up to possibly some combo of new farrier, new location, stress from trip, new feed (he likely has EPSM as a drafty and up in MD we were using a local high fat feed and down here in GA I had to come up with an alternative), and being out of shape.
However, this past weekend, we ended up working really hard on Sunday and I noticed the foot-sliding action returned again after as we were cooling out walking.
I've tried looking it up online but all my searches just give me references to sliding stops in reining which isn't what I want, obviously. Anybody here have any thoughts on what it might be?
Currently I'm leaning toward it being related to EPSM. :/
What type of ground/footing is he doing this on? Is there any ground he doesnt do it on? I would lean away from epsm becaus it tends to cause tightness not laxity. Those are in completely different directions!
Is he walking fast when he does this? I had a fresh off the track mare that did the same thing you describe for about 6 months when she was walking fresh and was adjusting to flat shoes (vs race plates with grabs built in). The mare has a gorgeous walk (by dressage standards) and the stride had a clear 5-6 hoof over track when not sliding. The sliding is clearly voluntary in her case (like it feels good) and can only occur on looser footings or concrete. It never concerned me other than thinking she could slip.
His stifles could be a little loose from being out of shape. I have one gelding that does it on certain footings or inclines and he has continuously loose stifles -- gets better as they tighten up. But probably hard to say without seeing it as I might be imaging something completely different then you are describing.