This is excellent advice. I do these things. While I'm mostly on my side in bed (with a pillow between my knees), I also put that pillow under my knees when I'm on my back. And on my side, I place a yoga bolster behind me to support my back. Finally, there is a pillow in front of me and I rest my arm on that when I'm on my side.

I'm 70 y/o with a diseased and degenerated lumbar spine. But through core strength, maintaining a weight slightly below normal, and my sleeping support I have no pain related to my lumbar spine. It's a lotta work, but it feels good, and beats back spasms, or worse, fusion surgery.