Quadratus lumborum muscle

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
Actions	Alone, lateral flexion of vertebral column; Together, depression of thoracic rib cage

The Quadratus lumborum is irregular and 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

Anterior to the Quadratus lumborum are the colon, the kidney, the Psoas major and (if present) psoas 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 four actions:

1. Lateral flexion of vertebral column, with ipsilateral contraction
2. Extension of lumbar vertebral column, with bilateral contraction
3. Fixes the 12th rib during forced expiration
4. Levates ilium, with ipsilateral contraction

Indications

The quadratus lumborum, or QL, is a common source of lower back pain.^[1] Because the QL connects the pelvis to the spine and is therefore capable of extending the lower back when contracting bilaterally, the two QLs pick up the slack, as it were, when the lower fibers of the erector spinae are weak or inhibited (as they often are in the case of habitual seated computer use and/or the use of a lower back support in a chair). Given their comparable mechanical disadvantage, constant contraction while seated can overuse the QLs, resulting in muscle fatigue.^[2] A constantly contracted QL, like any other muscle, will experience decreased bloodflow, and, in time, adhesions in the muscle and fascia may develop, the end point of which is muscle spasm.

This chain of events can be and often is accelerated by kyphosis which is invariably accompanied by rounded shoulders, both of which place greater stress on the QLs by shifting body weight forward, forcing the erector spinae, QLs, multifidi, and especially the levator scapulae to work harder in both seated and standing positions to maintain an erect torso and neck. The experience of "productive pain" or pleasure by a patient upon palpation of the QL is indicative of such a condition.

While stretching and strengthening the QL are indicated for unilateral lower back pain, heat/ice applications as well as massage and other myofascial therapies should be considered as part of any comprehensive rehabilitation regimen.^[3]

Additional images

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  Right hip bone. Internal surface.

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  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.

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  The abdominal aorta and its branches.

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  Horizontal disposition of the peritoneum in the lower part of the abdomen.

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  Transverse section, showing the relations of the capsule of the kidney.

References

1. ^ Clinical Orthopaedic Examination, Ronald McRae, 2004 (5th ed.).
2. ^ Core Topics in Pain, p.131, Anita Holdcraft and Sian Jaggar, 2005.
3. ^ McGill, S. Ultimate Back Fitness and Performance. Stuart McGill, PhD, 2004.

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"
• Stretching the Quadratus Lumborum
• Massaging the Quadratus Lumborum

This article was originally based on an entry from a public domain edition of Gray's Anatomy. As such, some of the information contained within it may be outdated.