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Quadratus lumborum: anatomy, physiology and involvement in back pain.

Quadratus lumborum (QL) is a central, square-shaped muscle belonging to the deep layer of the dorsolateral abdominal wall. The fibres of each QL run slightly diagonally from the rib and spine inferiorly and laterally towards the posterior ilia. QL resides in the area between psoas major and psoas minor muscles and the tendon of origin of transversus abdominis. It originates from the posterior iliac crest and the iliolumbar ligament and inserts on the transverse processes of L1-L4 and the inferior border of the 12th rib (see Figure 1). Its innervation is the ventral rami of T12-L4 and branches of the lumbar plexus.

The main actions of QL are to laterally flex the trunk when the muscle is contracted on one side. Contraction of both QLs extend the lumbar segment of the vertebral column. In addition, QL fixes the 12th rib during movements of the thoracic cage during forced expiration. QL also holds the 12th rib inferiorly in inspiration, thereby allowing the thoracic cage to expand fully. However, laboured breathing can be caused by QL dysfunction or imbalances in the postural muscles such as the erector spinae, abdominals and psoas muscles.

Functionally, QL positions the spine relative to the pelvis, and aids in maintaining an upright posture while co-ordinating with the erector spinae muscle group to create fine lateral movements and extension. On standing, the two QLs, in conjunction with gluteus medius, position the upper body over the lower body. While walking, QL and gluteus medius aid in pelvic stabilisation as body weight shifts from one foot to the other. In addition, QL lifts the iliac crest towards the thoracic cage as weight shifts to the other foot, which allows the leg to swing forward without the foot touching the ground.

QL and its relationship to back pain

Although there are many possible causes of back pain and discomfort, such as a herniated disk or sciatic nerve entrapment, QL in conjunction with weakness in the lower fibres of the erector spinae muscle fibres can cause the QL muscles to chronically contract bilaterally and with impending muscle fatigue result in an adaptive postural shift. This could be the case with long periods of computer use in a seated position, especially on a non-ergonomic chair.

Other problems associated with developing low back pain are decreased vascular flow, and the formation of adhesions in the muscle and fascia wrapping around muscle fascicles (perimysium) as well as fascia surrounding the whole muscle (epimysium). This chronic contraction of QL in the lower back can cause the fascial sheath to transmit a strain through the rest of the back and into the neck and shoulder regions. The other condition, which may result, is a developing muscle spasm which forcefully contracts when it becomes hyper-excitable. (1) Postural deviations such as kyphosis can aggravate back pain or lumbar discomfort by altering the body weight anteriorly, placing increased tension on QL and other muscles such as multifidus, levator scapulae and erector spinae in an attempt to maintain a correct centre of gravity. In this regard, it is very important to consider the body as a kinematic chain where a muscular or fascial shift in tension in one part of the body would be most likely to affect tension in the same tissues in a more distal part of the body.

Another problem with a tight QL is a condition that can develop during the leg swing phase in gait. It is called 'hip hiking'2 where a weak gluteus medius or gluteus minimus will force the QL in conjunction with tensor fasciae latae to become the compensatory prime movers of hip abduction. This results in excessive lateral compression on the lumbar segments of the spine.

Before any treatments are considered it is useful to assess muscle and postural imbalances (e.g. kyphosis, lordosis) which, if corrected, could reduce QL tension and the associated lumbar pain and/or discomfort. According to Reaves (3) clinical features could include an elevated pelvis on the side of pain and a lumbar area laterally flexed to the side of pain.

Some effective treatment techniques

Possible alternative therapy treatments include stretches in an attempt to return the fascia to a normal tension state and manually elongate the QL muscles that have adaptively shortened. Stretches could be applied passively, which elongates a shortened muscle-tendon unit and peri-articular connective tissues by moving a restricted joint a little past the existing ROM.

Another type of stretch is a proprioceptive neuromuscular facilitation (PNF) stretch, which reflexively relaxes tension in shortened muscles before or during stretching. Strengthening exercises of QL are recommended to aid in stabilising the pelvis relative to the lumbar segment of the spine.

Soft tissue mobilisation techniques include friction massage, myofascial release, acupressure and trigger point therapy. Trigger point therapy, according to Perry (4) can be used to treat intense, deep aching and, on occasions, a sharp stabbing pain which can refer to areas such as the hip joint, sacro-iliac joints, and lower gluteal regions. These mobilisations generally target connective tissue such as fascia, which can restrict muscle contractions and thereby affect movements.

In conclusion, postural dysfunction, which is a common problem today and which contributes to back pain and discomfort, can in part be addressed by targeting treatment towards quadratus lumborum.

Patrick de Permentier | BSc (Hons), UNSW, MSc (Research), UNSW, Grad Cert HEd (UNSW), Diploma Remedial Massage (NSW School of Massage).

Patrick de Permentier BSc (Hons), UNSW, MSc (Research), UNSW, Grad Cert HEd (UNSW), Diploma Remedial Massage (NSW School of Massage). Lecturer, Anatomy Department, School of Medical Sciences, Faculty of Medicine, UNSW. Lecturer in Anatomy and Physiology, NSW School of Massage, Sydney. ATMS Research Committee member, Council member ANZACA (Australian and New Zealand Association of Clinical Anatomists)

REFERENCES

(1.) MedicineNet, 2015. Muscle spasms. What a causes muscle spasms? [updated October 28, 2015], Available http://www.medicinenet.com/ m usde_spasms/page7. h tm

(2.) Kerrigan DC, Frates EP, Rogan S, Riley PO. Hip hiking and circumduction: quantitative definitions. Am J Phys Med Rehabil. 2000; 79 (3): 247-52.

(3.) Reaves W. Low Back Pain: The Quadratus Lumborum muscle., Pacific College of Oriental Medicine [updated October 22,2014], Available from: http://www.pacificcollege.edu/news/blog/2014/10/22/low-back-pain-quadratus-lumborum-muscle

(4.) Perry L. The Quadratus Lumborum Trigger Points: Masters of Low Back Pain, [updated 2011], Available from: http://www.triggerpointtherapist. com/blog/quadratus-lumborum-trigger-points/ql-trigger-points-master-slow-back

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Author:de Permentier, Patrick
Publication:Journal of the Australian Traditional-Medicine Society
Date:Dec 1, 2015
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