Well, in this day and age, I would think that to be sufficient warning...so no lasting injuries, but a lot to think about in terms of pain- bruises, armor bites, general soreness from hitting the ground backside first?
Hey, if we see one of those recalcitrant knights, I'm all for stripping him down to his undergarments and beating him with the flats of our blades right out of the town gates. lol