Rabbits have INCREDIBLY fragile bone structures, they can break their backs with one good kick if their backs are not supported.
This is true. I had a rabbit, a chocolate Dutch, when I was a kid, and that's how I lost him. I went out to the hutch one morning and he was paralyzed. Nothing had gotten into the hutch, but the vet's guess was that something frightened him in the night, he began tearing around the hutch and broke his back. They are incredibly beautiful little animals, but they are fragile.
My dog adored the rabbit. She'd follow (not chase) the rabbit around with a concerned look on her face. My tomcat, on the other hand, was a prime suspect in the 'who scared the rabbit to death' inquiry.