If one has to sleep on their back, is a lumbar pillow the best way to go for the lower back?

Having a pillow, or maybe a rolled up blanket, under the knees will take a lot of strain off the lower back. Experiment to see what feels the best.

I second a bolster under the knees. It will flatten out the back if the knees are bent.

I have to keep a pillow under or between my knees to deal with the sciatica. Trying unsuccessfully to avoid the disc surgery.

Oh, my aching back! Lumbar pillows have never been a help. I use a long body pillow, which I can put between my knees and ankles and still rest my head on.

A lumbar pillow will probably be of the most help when you are in a sitting position. Pillows behind your knees will relieve strain on your lower back and hips when you are lying on your back. The less your back is lifted off the mattress, the more the muscles can relax during sleep.
Wishing you comfort…...

If there is anyway you can sleep on either side, place at least two pillows in between your kness. i have had 4 back surgeries and i know all the tricks in the book. also, for the very best relief you will ever have for a lower back, lay flat on the floor on your back. raise your legs and place them in a chair and scoot your butt up next to the chair. blessed relief. this takes all the strain off your back and i expect you to be emailing me with a big thank you. john

@Austinlad Those long “body pillows” are great. @john65pennington I use a modified version of that, “flat back” with knees raised to the point that the soles of my feet rest comfortably on the floor. I’ve also got the “inversion boots” which is basically hanging yourself upside down by your ankles, decompressing the spine.