Quadratus lumborum muscle

Last revised by Calum Worsley on 2 Jun 2021

Citation, DOI, disclosures and article data

Citation:

Jarvis M, Worsley C, Haouimi A, et al. Quadratus lumborum muscle. Reference article, Radiopaedia.org (Accessed on 28 Nov 2023) https://doi.org/10.53347/rID-33837

DOI:

https://doi.org/10.53347/rID-33837

Permalink:

https://radiopaedia.org/articles/33837?iframe=true

rID:

33837

Article created:

25 Jan 2015, Matthew Jarvis

Disclosures:

At the time the article was created Matthew Jarvis had no recorded disclosures.

View Matthew Jarvis's current disclosures

Last revised:

2 Jun 2021, Calum Worsley ◉

Disclosures:

At the time the article was last revised Calum Worsley had no recorded disclosures.

View Calum Worsley's current disclosures

Revisions:

15 times, by 15 contributors - see full revision history and disclosures

Systems:

Musculoskeletal, Spine

Sections:

Anatomy

Tags:

anatomy; back; spine; muscle

Synonyms:

Quadratus lumborum muscles

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

Gross anatomy

Attachments

origin: medial half of inferior margin of 12th rib and upper four lumbar transverse processes
insertion: iliolumbar ligament and internal rim of iliac crest

Relations

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:

colon
kidney
psoas muscle (major and minor)
diaphragm
subcostal, ilioinguinal and iliohypogastric nerves

Arterial supply

The quadratus lumborum muscle is supplied by:

branches of the lumbar arter ies
the arteria lumbalis ima
the lumbar branch of the iliolumbar artery
branches of the subcostal artery

Innervation

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

Action

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 muscles contract, extension of the lumbar spine