Last Chance! Half price offer on our two latest online courses is about to end REGISTER NOW

Quadratus lumborum muscle

The quadratus lumborum muscle is a paired, irregular quadrilateral muscle that forms part of the posterior abdominal wall.

  • location: posterior abdominal wall
  • attachments: inferior margin of 12th rib and upper four lumbar transverse processes, iliac crest and iliolumbar ligament
  • blood supply
    • branches of the lumbar arteries
    • other smaller arterial branches, as described below
  • innervation
    • ventral rami of the 12th thoracic nerve
    • L1-L4 spinal nerves
  • action: extension and lateral flexion of vertebral column; fixes 12th rib during inspiration to stabilize the diaphragm
  • origin: medial half of inferior margin of 12th rib and upper four lumbar transverse processes
  • insertion: iliolumbar ligament and internal rim of iliac crest

The muscle is a thick, irregular, quadrilateral-shaped muscle sheet that lies in the posterior abdominal wall on each side of the lumbar vertebrae. It is superficial to the psoas major muscle.

Anterior relations include:

The quadratus lumborum muscle is supplied by:

  • ventral rami of the 12th thoracic nerve
  • L1-L4 spinal nerves

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 vertebral column 
  • when both sides contract, extends the lumbar spine
  • extent of attachment to the last rib varies
  • implications in unilateral lower back pain
  • may be enlarged in cricket fast bowlers who injure their L4 pars interarticularis 3
Anatomy: Spine
Anatomy: Abdominopelvic

Anatomy: Abdominopelvic

Article information

rID: 33837
Section: Anatomy
Synonyms or Alternate Spellings:
  • Quadratus lumborum muscles

ADVERTISEMENT: Supporters see fewers/no ads

Cases and figures

  • Figure 1
    Drag here to reorder.
  • Figure 2
    Drag here to reorder.
  • Figure 3
    Drag here to reorder.
  • Updating… Please wait.

     Unable to process the form. Check for errors and try again.

     Thank you for updating your details.