Sleeping on your back
If you sleep on your back, place a pillow under your knees to help maintain the normal curve of your lower back. You might try a small, rolled towel under the small of your back for additional support. Support your neck with a pillow.
This position may be helpful if you have low back pain.
Sleeping on your abdomen
Sleeping on your abdomen can be hard on your back. If you can't sleep any other way, reduce the strain on your back by placing a pillow under your pelvis and lower abdomen. Use a pillow under your head if it doesn't place too much strain on your back. If it does cause strain, try sleeping without a pillow under your head.
This position may be helpful if you have degenerative disease or a herniated disk in the central portion of your spine.
Mattresses and recliners
What you sleep on can also affect how comfortably you sleep. If adjusting your sleeping position doesn't help reduce back pain, try adjusting your sleeping surface. Mattress firmness is an individual choice. If you have chronic low back pain, you may benefit from sleeping on a medium-firm mattress. Consider trying out a medium-firm mattress before you buy. However, you may find your back pain is reduced with a softer mattress.
If you have bursitis in your hips, you may find that a foam mattress pad reduces pain. And sleeping in an adjustable bed or reclining chair that keeps your head and knees up may help with low back pain.