Just going from your description, I am imagining a horse that stands similar to the horse pictured in D
And he has a gait that is similar to this
It isn't that uncommon of a fault though it is far from ideal. It causes more wear on the joints and they can suffer injuries from banging themselves with the hind foot in motion. So long as you use protection to keep that from happening (like your vet said, use boots), then the biggest concern to me will be arthritis.

And he has a gait that is similar to this

It isn't that uncommon of a fault though it is far from ideal. It causes more wear on the joints and they can suffer injuries from banging themselves with the hind foot in motion. So long as you use protection to keep that from happening (like your vet said, use boots), then the biggest concern to me will be arthritis.