There is a C-clip on the back side of the knob that you need to pull out. You should be able to pull it out with a pair of needlenose pliers or pry it out with a flathead screwdriver. Once you do that, the knob should pop right off.
After cutting mine off with a steak knife as a last resort(haha)....I was told there is a pin in there somewhere....my friend took his off no problem so it will come off if you can just find it