My newest advice is don't sit with your legs crossed. The reason for this with my bad knees is that the amount of torque that is put on your tibia when you do that is very high. My right knee (the one with the partially torn ACL) popped and I couldn't move or straighten my leg. It took about 15 minutes before it started to feel better.
I asked the physical therapist at the gym. He was the one who told me I shouldn't sit with my legs crossed.
So if I sit down on the floor, how am I supposed to sit? I can't sit with my legs out straight. I can't bend them to one side because my back would complain. Don't even think about kneeling. That is not possible. I can't stop sitting on the floor either. Sometimes you just need to sit down an take care of something.
All I can say is crap!