You pull your knees out of the way so you don’t shave off your knee caps and then you push your knees forward again so that you can launch the bar upward. If you ONLY pull your knees back then you run into the problem of being straight legged when you go to throw the bar. This usually means you’ll resort to arm strength. If you don’t pull your knees out of the way it means you’ll either nail your knees or you’ll swing the bar away from yourself and then back into yourself.
So many things to go wrong, right? Right. Get your knees out of the way and then get them back into the right place.
Want to see the whiteboard and the workout? Go here.