Low back pain cases we treat in our Beaverton clinic, often include soft-tissue release of the psoas muscles, more commonly called the hip flexor.
As you can see from the above image, the psoas muscle has attachment points on the spine, and as such is often a contributor to low back pain and anterior pelvic rotation. Similar to the shortening that occurs in the shoulders and chest muscles from too much time at the computer, shortening of the hip flexors is very common from extended time spent sitting.