Having a bone in my hand set without anesthetic, I suspect it's because when a broken bone becomes rapidly agitated it's causing a bunch of nerves to fire their

Having a bone in my hand set without anesthetic, I suspect it's because when a broken bone becomes rapidly agitated it's causing a bunch of nerves to fire their pain signals. The tuning fork most likely resonates the bone rapidly -- if things are just sprained, the whole bone vibrates. If the bone is broken, it grinds against itself.