I came here specifically to say what @Sarah616 did about EDM.
I just got home from walking a course. My ankle hurts now. It’s hurt for about a year now. It will likely hurt for a long, long time.
I don’t remember why it hurts–that is to say, I don’t remember hitting the ground on it, ripping the soft tissue, and then falling and hitting my head. I just remember swinging a leg over to tack-walk, sticking three immediate bronc bucks, failing to stick the fourth, and getting up to limp after her as she scrambled away panicking so hard she pulled a shoe.
I’ve had a lot of horse-related injuries, but that’s the only one I don’t remember.
She, too, started off the whole affair with a hind toe drag.
And I, too, wish she could have been a pasture pet forever.
But if your boy does have EDM–and I fervently, fervently hope that he does not–it is very unlikely that he will remain safe on the ground forever. Or even, perhaps, for very long. And he might hurt you, or the farrier, or the vet, or a barn staff member if you board… but he also might hurt himself out of sheer blind panic when there’s no one there to help.