Quadratus lumborum muscle
The relations of the kidneys from behind. (Quadratus lumborum visible at lower left.)
Deep muscles of the back. (Quadratus lumborum visible at bottom left.)
Latin	musculus quadratus lumborum
Gray's	subject #118 420
Origin	iliac crest and iliolumbar ligament
Insertion	Last rib and transverse processes of lumbar vertebrae
Artery	Lumbar arteries, lumbar branch of iliolumbar artery
Nerve	The twelfth thoracic and first through fourth lumbar nerves
Action	Alone, lateral flexion of vertebral column; Together, depression of thoracic rib cage
Dorlands /Elsevier	m_22/12550391

The Quadratus lumborum is irregularly quadrilateral in shape, and broader below than above.

Origin and insertion

It arises by aponeurotic fibers from the iliolumbar ligament and the adjacent portion of the iliac crest for about 5 cm., and is inserted into the lower border of the last rib for about half its length, and by four small tendons into the apices of the transverse processes of the upper four lumbar vertebrae.

Occasionally a second portion of this muscle is found in front of the preceding. It arises from the upper borders of the transverse processes of the lower three or four lumbar vertebræ, and is inserted into the lower margin of the last rib.

Relations

In front of the Quadratus lumborum are the colon, the kidney, the Psoas major and minor, and the diaphragm; between the fascia and the muscle are the twelfth thoracic, ilioinguinal, and iliohypogastric nerves.

Variations

The number of attachments to the vertebræ and the extent of its attachment to the last rib vary.

Actions

The quadratus lumborum can perform three actions:

1. Lateral flexion of vertebral column, with ipsilateral contraction
2. Extension of lumbar vertebral column, with bilateral contraction
3. Fixes ribs for forced expiration

Additional images

Right hip bone. Internal surface.	Diagram of a transverse section of the posterior abdominal wall, to show the disposition of the lumbodorsal fascia.	The diaphragm. Under surface. Quadratus lumborum visible at lower right.
Muscles of the iliac and anterior femoral regions.	The lumbar plexus and its branches.	The abdominal aorta and its branches.
Horizontal disposition of the peritoneum in the lower part of the abdomen.	Transverse section, showing the relations of the capsule of the kidney.

External links

• LUC ql
• -1234501552 at GPnotebook
• quadratus+lumborum+muscle at eMedicine Dictionary
• Atlas of anatomy at UMich abdo_wall70 - "Posterior Abdominal Wall, Dissection, Anterior View"

This article was originally based on an entry from a public domain edition of Gray's Anatomy. As such, some of the information contained herein may be outdated. Please edit the article if this is the case, and feel free to remove this notice when it is no longer relevant.

This muscle article is a stub. You can help Wikipedia by expanding it.