Blood Supply of Quadratus Lumborum Muscle

Last updated: February 7, 2026Reviewed date: February 7, 2026Reading time: 5 min read
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Article Summary

Blood Supply of Quadratus Lumborum Muscle/Quadratus Lumborum Muscle informally called the QL, is a paired muscle of the left and right posterior abdominal wall. It is the deepest abdominal muscle and commonly referred to as a back muscle. Each is irregular and quadrilateral in shape. The quadratus lumborum muscles originate from the wings of the ileum; their insertions are on the transverse processes of the...

Key Takeaways

  • This article explains Origin And Insertion of Quadratus Lumborum Muscle in simple medical language.
  • This article explains Blood Supply of Quadratus Lumborum Muscle in simple medical language.
  • This article explains Nerve Supply /Innervation of Quadratus Lumborum Muscle in simple medical language.
  • This article explains Functions of Quadratus Lumborum Muscle in simple medical language.
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Blood Supply of Quadratus Lumborum Muscle/Quadratus Lumborum Muscle informally called the QL, is a paired muscle of the left and right posterior abdominal wall. It is the deepest abdominal muscle and commonly referred to as a back muscle. Each is irregular and quadrilateral in shape. The quadratus lumborum muscles originate from the wings of the ileum; their insertions are on the transverse processes of the upper four lumbar vertebrae plus the lower posterior border of the twelfth rib. Contraction of one of the pair of muscles causes lateral flexion of the lumbar spine, the elevation of the pelvis, or both. Contraction of both causes extension of the lumbar spine.

The quadratus lumborum (QL) muscle resides in the deep and posterior, lateral and inferior areas of the spine, involving the iliac crest, the transverse processes of the lumbar vertebrae and the 12th rib. The muscular organization is complex, and it is difficult to identify precisely the actions that occur through the contraction of fibers. It is an integral part of the thoracolumbar fascia. There is still no certainty that an abnormality of QL is the primary source of back pain. The QL could potentially act as a crossroad of the forces exerted by the neighboring muscles, influencing the vectors of the different tensions produced. Thanks to its strategic position and the entropic scheme of its fibers, QL is a significant means of access for anesthesia, during surgery on the back, lower limbs or abdominal area. The article reviews the latest anatomical and clinical information on the quadratus lumborum.

Blood Supply of Quadratus Lumborum Muscle

Attachments

  • The medial half of inferior margins of 12th ribs and upper four lumbar transverse processes. Iliac Crest (specifically the top and back part of the pelvis) The bone at the top and back of the pelvis is known as the Ilium.
  • Transverse processes (bony parts that stick out to the side of each vertebra) of lumbar vertebrae usually just the top four lumbar vertebrae
  • The 12th rib (That’s the last rib, also known as a floating rib because it does not attach to the rib cage)
  • Origin – medial half of inferior margins of 12th ribs and upper four lumbar transverse processes. It starts from the iliac crest of the ilium and runs craniomedially, attaching to the 12th rib and the transverse processes of the 1st to 5th lumbar vertebrae. All fibers together give the muscle a rectangular appearance.
  • Location – dorsal abdominal wall
  • Insertion – iliolumbar ligament and internal rim of the iliac crest

Relation

  • The muscle is a thick, irregular, quadrilateral-shaped muscle sheet that lies in the posterior abdominal wall. Thick, irregular, quadrilateral-shaped muscle sheet that lies in the posterior abdominal wall with related to,
  • 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.


The quadratus lumborum muscle is supplied by

  • Branches of the lumbar arteries
  • Other smaller arterial branches, as described below
  • Branches of the lumbar artery
  • The arteria lumbalis ima
  • The lumbar branch of the iliolumbar artery
  • Branches of the subcostal artery
  • Anterior branches of the ventral rami of T12 to L4.
  • Ventral rami of the 12th thoracic nerve
  • L1-L4 spinal nerves

Functions of Quadratus Lumborum Muscle

The quadratus lumborum can perform four actions:

  • Extension and lateral flexion of the vertebral column; fixes 12th rib during inspiration to stabilize the diaphragm
  • To bring the ribs closer to the pelvis on the same side, known as lateral flexion
  • It’s often referred to as the “hip hiker” as it can lift the pelvis toward the lower ribs on the same side.
  • Lateral flexion of the vertebral column, with ipsilateral contraction
  • Extension of the lumbar vertebral column, with bilateral contraction (based on a line of force passing ~3.5 cm posterior L3 rotation axis[rx])
  • Fixes the 12th rib during forced expiration. The quadratus lumborum assists the diaphragm in inhalation
  • Elevates the Ilium (bone), with ipsilateral contraction (“hip hiking”)

Additional functions

  • Vertical stabilization of pelvis, lumbar spine, and lumbosacral junction. Prevents collapse of the vertebral column in the frontal plane (i.e. scoliosis)
  • Reserve mover actions: Anterior pelvic tilt. Contralateral lateral pelvic rotation.

Multiple actions, including

  • Muscle of inspiration
    • fixation of the last rib
    • stabilization of lower attachments of the diaphragm
    • proposed to provide a base for controlled diaphragmatic relaxation to facilitate precise adjustments required for speech and singing 1
  • When one muscle contracts, lateral flexion of the vertebral column
  • When both sides contract, extends the lumbar spine.


References

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