There are various reasons why someone suffers from a low back pain . These reasons might be related to the nerves, bones, muscles, joints, ligaments, etc.
Out of all those reasons, one of the most common muscle related cause is the tightness or possibly a trigger point in one of the muscles in your low back area which is called Quadratus Lumborum or QL. This muscle is attached from your lowest rib (Rib #12) to the top of your hip bone, and its functions are to stabilize your core and rib, to lift your hip bone and to bend your torso towards the same side.
Sitting for a long time, sudden twisting moves, carrying your child with one arm, reaching for objects far from your body when you lift them, are some examples of how you can injure this muscle which can result in a low back pain. The trigger points of this muscle can also create referral pain inside your buttock as shown in these images
Stretching this muscle frequently, can improve the health of the tissues around this muscle and reduce the chance of tightness, trigger point, and muscle imbalance. The fibers of this muscles are positioned in different directions and so finding the best position to stretch this muscle might be challenging for a lot of people. I've included a link to a video which explains how to stretch QL muscle effectively. Stretch this muscle 3 times/week, each time for 2 sets of 30 seconds.
Hooman Jamshidi Founder @Dur1 Health Registered massage therapist (RMT), Certified personal trainer, Student Acupuncturist