I’ve had TKR, but didn’t have that problem. But when first went on my Bipap several years ago couldn’t get used to it. A friend that was a respiratory therapist suggested go to sleep with out it and when I wake up cause I’d wake up couple times a night, put it on. Since I was in sort of a sleep mode I might fall back to sleep with it on. That worked for me. I got used to having it on and was able to put on when I first went to bed.