I have THR and both knees replaced. I have always used a knee pillow. I am currently four months out my recent TKR left side. If I don't have the pillow from my knee to ankle I feel my hip angle is to low and I have pain in my knee. My pillow is pretty flat. I don't like the feel of my knees touching. I have always been told to use a pillow. I just know I am uncomfortable without it.