First of all I must ask why you need the knob off the backrest adjustment rod? Is it because you are kaking the chrome facing off to replace, or are you wanting to just get another knob? If you are wanting to take the chrome off, you don't need to remove the knob from the rod. You just need to go to the back of your seat and remove the panel, then remove the clips that keep the rod in place, then slip out the rod with knob intacted, then just remove the chrome facing.
Bob