actress lucy lawless ended up with a fractured pelvis when a horse fell on her. iirc it happened in a parking lot outside of where they used to shoot the jay leno show.
if that’s right, she’d’ve been better off had it been something other than a hard surface like asphalt or concrete they landed on. i’ve fallen a couple of times off of horses during training but landing on three or four feet of fluffy tanbark instead of hard ground makes a big difference.
My daughter rode in hunter/jumper shows. She never had a horse fall on her (though one bit her) but I’ve seen it happen. Once a leg was broken, mostly no injuries at all. But it depends on the circumstances.