Quadratus lumborum muscle (2024)

Author: Achudhan Karunaharamoorthy, MDReviewer: Dimitrios Mytilinaios, MD, PhD
Last reviewed: October 30, 2023
Reading time: 5 minutes

Quadratus lumborum muscle (1)

Recommended video: Muscles of the trunk[21:21]

Main muscles of the thorax, abdomen and back.

The quadratus lumborum muscle is a muscle of the posterior abdominal wall lying deep inside the abdomen and dorsal to the iliopsoas. It is the deepest muscle of the posterior abdominal wall, and it is often mistakenly referred to as one of the muscles of the back. Its shape is irregular, but is generally quadriangular, which is the reason why it is described as 'quadratus' in latin.

Besides the spine, it also attaches to the twelwth rib, which makes it very important for stabilization of bothvertebral columnand the rib during various movements of the spine. In order to palpate the muscle one needs place the fingers above the posterior iliac crest at the level of the hip.

This article will discuss the anatomy and clinical importance of the quadratus lumborum muscle.

Key facts about the quadratus lumborum muscle
OriginIliac crest, iliolumbar ligament
InsertionInferior border of rib 12, transverse processes of vertebrae L1-L4
InnervationSubcostal nerve (T12), anterior rami of spinal nerves L1-L4
Blood supplyLumbar, median sacral, iliolumbar and subcostal arteries
FunctionBilateral contraction - fixes Ribs 12 during inspiration, trunk extension
Unilateral contraction - lateral flexion of trunk (ipsilateral)


  1. Originand insertion
  2. Relations
  3. Innervation
  4. Blood supply
  5. Function
  6. Clinical aspects
  7. Sources

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Originand insertion

Quadratus lumborum originates from the iliolumbar ligament and iliac crest. It runscraniomedially, attachingto the inferior border of12th riband the transverse processes of the 1st to 4th lumbar vertebrae. All fibers together give the muscle a rectangular appearance.


The quadratus lumborum fills a great amount of space within the abdomen and is therefore in close proximity to many structures. The colon, the kidneys and the diaphragm are located ventrally to the muscle, whereas the intrinsic back muscles lie dorsomedially.

Both the iliohypogastric and ilioinguinal nerves course on the ventral surface of the quadratus lumborum after exiting the lumbar plexus and continue towards the lateral abdominal muscles.

Looking for a fast and effective way to consolidate your knowledge on the quadratus lumborum? With charts listingthe attachments, innervations and functions of every muscle, our trunk wall muscle chart is an essential revision tool.


Quadratus lumborum is innervated by the subcostal nerve (T12) and anterior rami of spinal nerves L1-L4.

Blood supply

Blood supply to quadratus lumborum comes from thebranches of lumbar, subcostal,median sacral, andiliolumbar arteries.

Subcostal nerve

Nervus subcostalis


Synonyms: Anterior ramus of spinal nerve T12, Ramus anterior nervi spinalis T12


Essentially, the quadratus lumborum contributes to the stabilization andmovement of the spineand the pelvis. A bilateral contraction leads to an extension of the lumbar vertebral column. When the muscle is only activated on one side, the trunk is bent towards that direction (lateral flexion).

In addition, the muscle fixes the 12th rib during movements of the thoracic cage and this way supports expiration (accessory muscle of expiration).

Learn everything about the muscles of the abdominal wall with our articles, video tutorials, quizzes and labeled diagrams.

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...or if you're feeling ready to test your knowledge right away, try out our abdominal muscles quiz!

Clinical aspects

Overuse and strain of the quadratus lumborum are one of the major causes for chronic pain in the lower back. One typical cause is the habit of sitting at the desk using a reclined seat, which releases the intrinsic back muscles and weakens them in the long term. The weak back muscles must now be compensated by the quadratus lumborum leading to painful tension and stiffening of the muscle.

Other causes can be direct damage or any type of imbalance of the pelvis or spine which forces the quadratus lumborum to stabilize them. An example of that type of imbalance is unequal leg lengths.


All content published on Kenhub is reviewed by medical and anatomy experts. The information we provide is grounded on academic literature and peer-reviewed research. Kenhub does not provide medical advice. You can learn more about our content creation and review standards by reading our content quality guidelines.


  • D. Drenckhahn/J. Waschke: Taschenbuch Anatomie, 1st edition, Urban & Fischer Verlag/Elsevier (2008), p. 145
  • M. Schünke/E. Schulte/U. Schumacher: Prometheus – LernAtlas der Anatomie – Allgemeine Anatomie und Bewegungssystem, 2nd edition, Thieme Verlag (2007), p. 152 G.
  • Fors: Why we hurt – a complete physical and spiritual guide to healing your chronic pain, Llewellyn Publications (2007), p. 135-138
  • Cael, C. (2010). Functional anatomy: Musculoskeletal anatomy, kinesiology, and palpation for manual therapists. Philadelphia, PA: Wolters Kluwer Health/Lippincott, Williams & Wilkins.
  • Moore, K. L., Dalley, A. F., & Agur, A. M. R. (2014). Clinically Oriented Anatomy (7th ed.). Philadelphia, PA: Lippincott Williams & Wilkins.
  • Netter, F. (2019). Atlas of Human Anatomy (7th ed.). Philadelphia, PA: Saunders.
  • Palastanga, N., & Soames, R. (2012). Anatomy and human movement: structure and function (6th ed.). Edinburgh: Churchill Livingstone.
  • Standring, S. (2016). Gray's Anatomy (41st ed.). Edinburgh: Elsevier Churchill Livingstone


  • Quadratus lumborum muscle (Musculus quadratus lumborum) - Yousun Koh

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Quadratus lumborum muscle (2)Kim Bengochea, Regis University, Denver

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Quadratus lumborum muscle (2024)
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