Your back muscles connect to your butt muscles, which then connect to your hamstrings, etc … Taking tension off your legs will then relax your back slightly. So, if you’re laying on your back and put something under your knees, for example, this will flex the knees, decreasing leg and back tension. Your hamstring muscles become shortened and relaxed lowering tension in your gluts and therefore your lower back.
On your side, a pillow between the knees will keep your legs and pelvis level. Think about being on your side if one leg flops well over the other, your pelvis is forced into rotation. The name of the game is to keep pressure off of nerves, and keeping the spine in alignment does this.
“How does a Pillow Under or Between my Knees Help my Back?”
CT Chiropractor Blog Post - October
One more thing to keep in mind, just like the muscles, but is true for the spine as well, is that it's completely connected. For example, if your cervical curve (neck alignment) is just right then your thoracic curvature maintains better alignment. The lumber spine then can stay in good position. That being said, it's a good idea to use a chiropractic neck pillow too.
These are a couple tricks with a pillow to help keep your back relaxed and without nerve pressure, therefore without pain. Happy sleeping!
Black Foam RollerThis positioning foam roll retains its shape after heavy use so you do not have to worry about ruining it.
Body Sport Foam RollerThe Body Sport Roller is a strong, high-density foam roller. It is great for ankle stretching and knee rehabilitation and can also be used as a balance board. This product can be used as a progressive exercise system ranging from easier to more difficult.
Jackson Roll PillowThe Jackson Roll Pillow is an incredibly versatile travel pillow that can provide lumbar support, cervical support, or knee support depending on how you want to use it.
Knee ElevatorThe Knee Elevator pillow is designed to fit perfectly under your knees while you are sleeping. This will reduce tension from your lower back while also improving circulation- all while you sleep! This pillow is also great for anyone with knee problems who want extra support while resting.