Another thing to consider is any significant load or if the load gets stuck, the line is gonna be right across your leg, horse snatches forward guess what? Your leg gets mashed into the horse even harder. SOunds like a recipe for disaster and probably why you see ropers back up from loads.
Actually, that is completely backward. If the load is heavy, then the horse needs to be facing forward, away from the rope because horses have limited power going backward (but you shouldn't be pulling anything terribly heavy on a young horse anyway until they get the hang of it). The only time you will see a roper facing what they are dragging is when they are stopped and simply holding the pressure on it. The only time they will back up instead of turning and facing the other way is if they just need to take a couple of steps to keep the rope tight.
In this picture, the rope had come tight and we were beginning to face up. That is why his left hind leg is stepping sideways instead of forward.
If the load gets stuck, then you need to stop pulling altogether until the load gets unstuck. If a load is stuck and you keep asking a young horse to pull, when they realize that they can't and they quit on you, you're screwed because you'll have trouble getting them to really pull again. That is why it is so important that you tell them to stop before they have to quit on their own.
About the leg thing, yes, your leg will get smashed, yes it is going to hurt, and yes, you will be bruised, but that's just a part of roping/dragging off of horses. When I work calves in the springtime, my right leg just pretty much stays
a lovely blue shade until it's all done.
Now, back to the OP. Ditto everything that Chick and Bsms said.
Also, while it is exceptionally handy to have a knife at all times for various reasons, the only time I've ever seen a roper end up in a bad enough wreck to need it was when he was tied off to the horn (where you tie a knot in the tail of your rope and tie it to the horn. You cannot get it off once there is pressure on it). His horse freaked and he ended up with the rope around his back, which basically seat-belted him into the saddle, then the horse got his legs tangled and went down. All of this with a cow on the end of the rope that weighed about 800. The guy managed to get his knife out and cut the rope loose and the cow proceeded to pull it the rest of the way off of them so that they could get up.
All that being said, I prefer to pull stuff from the saddle as opposed to on the ground just because I feel like I have better control of them that way. I used to have a couple of big old logs that had been lashed together that I used but at some point while I was living in Amarillo, those disappeared somewhere so nowadays I use this.