I’d euthanize. It sucks, for everyone involved, but given the circumstances it is totally reasonable.
The horse is only 4 and already in pain/has fairly severe limitations on its future as a riding horse. The rearing is also dangerous and again, limits the prospect as a riding horse. Rearing is likely due to pain in this situation. Take the initiative and bring up euthanasia, don’t wait for the vet to bring it up.
Let’s be real for a minute: how many people out there are looking for an unsound young horse that to even make remotely sound needs maitenance, again at age 4, and has a potential rearing problem? Even if someone is looking for a pasture puff or companion, they want one with very little to no maitenance. When there is a not a market for a horse, their fait is usually not so great when put up for sale or put at auction.
Are there any vet schools or the like in your area? You could inquire about donating the body for educational purposes if there is a need.
@TWH Girl What do you propose is doing right by this animal?