Quadratus Lumborum is a deep lower back muscle that connects from the top of the hip (Iliac Crest) to the bottom of the ribcage (12th rib). Quadratus Lumborum also connects to lumbar vertebrae in criss-cross like patterns . When it comes to lower back pain relief, Quadratus Lumborum tightness and trigger points should be investigated first because it is non-invasive, inexpensive, and could fix the problem quickly .
Quadratus Lumborum Anatomy & Function
Quadratus Lumborum Muscle:
Quadratus Lumborum Muscle (Rear Body View)
As shown above, Quadratus Lumborum connects from the top of the hip to the lowest rib, and also connects to lumbar vertebrae. Quadratus Lumborum lies underneath the long spinal erector muscles (backstrap muscles that run from the tailbone to the neck), and also underneath Latissimus Dorsi (lats - the wing-like back muscle that works during pull-ups). Quadratus Lumborum is also referred to as the deepest abdominal muscle .
Quadratus Lumborum Function:
The main function of Quadratus Lumborum is to keep the lumbar spine stable and safe . Quadratus Lumborum is very active during high impact sports because it needs to be in order to keep the lower back neutral and strong. Without Quadratus Lumborum, one sharp cut in a sport like basketball could result in a back fracture or disc herniation.
Quadratus Lumborum also functions in side bending and spinal extension. When carrying a heavy suitcase with one arm, the opposite side Quadratus Lumborum muscle fires to keep the body upright. One Quadratus Lumborum contracting in isolation will side-bend the spine, but both Quadratus Lumborum muscles contracting together results in spinal extension (arching the low back).
Quadratus Lumborum Pain Symptoms
Quadratus Lumborum pain will generally fell like vague low back pain. Lifting weights that were once easy will be difficult and uncomfortable, especially uneven weights that require strong spinal stability from Quadratus Lumborum.
Quadratus Lumborum Pain Pattern Chart 
The image above illustrates the referred pain patterns as depicted by Travell & Simons . Quadratus Lumborum pain can be felt in the low back, tailbone, and outer hip.
Quadratus Lumborum Pain Relief
Quadratus Lumborum pain relief can be felt with deep muscle release of trigger points and tightness. Knots and tightness can cause a lot of pain due to the constant muscle tension they maintain - constant muscle tension means the muscles are ALWAYS pulling on joints, compressing nerves, and preventing full range of motion through the muscle .
Deep tissue release of Quadratus Lumborum can be occasionally felt with a lacrosse ball, but a versatile, targeted massage tool like QL Claw is best. QL Claw was designed to release the 5 muscles that contribute to low back pain (and more), and Quadratus Lumborum is at the top of the list.
Quadratus Lumborum Pain Prevention
After releasing trigger points and tightness in Quadratus Lumborum, we want to strengthen the muscle to prevent further injury in the future. It is important to release trigger points and tightness first, because the constant muscle tension will not go away with strengthening.
A few strengthening exercises that are great for building a bulletproof Quadratus Lumborum are side planks, suitcase carries (one arm farmers carries), and side hyperextensions. Check out the strengthening portion in the video below for a side plank tutorial inspired by the back doctor Stuart McGill himself. Stuart McGill's side plank variation is awesome for not only building Quadratus Lumborum strength, but endurance as well. Endurance is key in sports because we want Quadratus Lumborum to be strong and stable from start to finish, not just for one heavy movement.
 Donnelly, Joseph M. Travell, Simons & Simons Myofascial Pain and Dysfunction: the Trigger Point Manual. 3rd ed., Wolters Kluwer Health, 2019.
 Davies, Clair, and Amber Davies. The Trigger Point Therapy Workbook: Your Self-Treatment Guide for Pain Relief. 3rd ed., New Harbinger Publications, Inc., 2013.