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.
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
The number of attachments to the vertebræ and the extent of its attachment to the last rib vary.
The quadratus lumborum can perform three actions:
- Lateral flexion of vertebral column, with ipsilateral contraction
- Extension of lumbar vertebral column, with bilateral contraction
- Fixes ribs for forced expiration
The quadratus lumborum, or “QL,” is a common source of lower back pain. 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
. A constantly contracted QL, like any other muscle, while 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.