The uncooperative roxy spin

I've been wanting to master the pretzel spin forever. It was the first pole dance "trick" I ever saw, and I thought, "oh that's so pretty!" I can do the first part of reverse grab, but wrapping my body around the pole just isn't working. An instructor from a different studio suggested I might try the roxy to gain flexibility. I cannot(currently) do this spin! I've been working on it for two months and it's so aggrivating when all of my other more adv moves (see hip hold to superman) I can get through in about two weeks. The issue seems to be my knee slipping. I've tried this spin so many times, and when I get my leg in the right position after getting over my fear of banging of bangin my side, my leg just refuses to stick. I hang there awkwardly (and with much pain) by my elbow. Eventually I develope a bruise and have to hang up the spin for a week or so until the bruise fades. Rinse and Repeat. I'm all ears and willing to try anything.