Understood, but here's a short list of beginner poses I shouldn't do:
Basically anything which involves holding my arms at or above my shoulders. So for a yoga class to be safe, I could do corpse pose, stand on one leg, stand on two legs... and that's about it. No weight on my shoulders. No raising my arms.
I tried doing yoga to alleviate the pain before I stayed getting treatment. Turns out it was one of the worst things I could have done. Yoga is great if your body can take it, but it is not the all-access panacea it's made out to be. I'm better off doing modified Pilates or tai chi -- something where you keep moving smoothly.