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| quadratus lumborum | |
|---|---|
| Name | Quadratus lumborum |
| Latin | Musculus quadratus lumborum |
| Origin | Posterior iliac crest, iliolumbar ligament |
| Insertion | 12th rib, transverse processes of L1–L4 |
| Blood supply | Lumbar arteries, iliolumbar artery, subcostal artery |
| Nerve | Ventral rami of T12–L4 (subcostal nerve, lumbar plexus branches) |
| Action | Lateral flexion of vertebral column, stabilization of 12th rib and lumbar spine |
| Antagonist | Rectus abdominis, psoas major |
quadratus lumborum is a deep posterior abdominal wall muscle located between the iliac crest and the 12th rib that contributes to stabilization and movement of the lumbar spine and thoracolumbar fascia. It lies posterior to the psoas major and anterior to the erector spinae and interacts with surrounding structures involved in posture and respiration. Clinically it is implicated in low back pain, respiratory mechanics, and operative approaches to the retroperitoneum.
The muscle arises from the posterior iliac crest and iliolumbar ligament and inserts on the inferior border of the 12th rib and transverse processes of L1–L4, coursing in proximity to the thoracolumbar fascia, psoas major, and quadratus lumborum may be bordered superiorly by the diaphragm and laterally by the transversus abdominis aponeurosis. Its anatomical relations include neighboring structures such as the kidneys, ureters, diaphragm crura, and lumbar plexus components; historically, dissections by Vesalius and anatomical atlases from Gray’s and Netter’s illustrate these intimate relationships. Variations in fascial attachments and slips have been documented in anatomical surveys and comparative studies across populations and in classic texts by Galen and Harvey.
Quadratus lumborum acts bilaterally to assist in lumbar extension and unilaterally to produce lateral flexion of the vertebral column while stabilizing the 12th rib during inspiration, interacting functionally with the diaphragm, internal oblique, and transversus abdominis during respiratory and postural tasks. It also contributes to pelvic stabilization during gait and load transfer between the pelvis and thorax, a role evaluated in biomechanical studies from institutions such as the Mayo Clinic, Johns Hopkins University, and Harvard Medical School. Athletic populations including runners, rowers, and weightlifters often recruit this muscle for trunk control, described in sports medicine literature from the International Olympic Committee and FIFA Medical Centre guidelines.
Innervation typically derives from the ventral rami of T12 to L4, including the subcostal nerve and contributions from the lumbar plexus; textbooks from Oxford University Press and Thieme document this pattern and occasional accessory innervation variants noted in cadaveric series at UCLA and the University of Toronto. Arterial supply arises from lumbar arteries, the iliolumbar artery, and branches of the subcostal artery; venous drainage follows corresponding lumbar veins that communicate with the azygos and hemiazygos systems described in classical cardiovascular atlases and surgical manuals used at Stanford and Cleveland Clinic. Knowledge of neurovascular relations is referenced in operative approaches by institutions such as the Royal College of Surgeons and Society for Vascular Surgery.
Quadratus lumborum dysfunction is implicated in chronic low back pain presentations evaluated in clinical trials at the Cochrane Collaboration, National Institutes of Health, and World Health Organization reports, and is a common target in manual therapy by practitioners trained at institutions like the British School of Osteopathy and the American Physical Therapy Association. Myofascial trigger points, spasms, and denervation may produce referred pain patterns overlapping with renal colic, lumbar radiculopathy assessed by the American Academy of Neurology, and sacroiliac joint dysfunction; differential diagnosis often involves imaging protocols from the American College of Radiology and consensus statements from the European Society of Radiology. Interventional management includes local anesthetic injections, radiofrequency ablation, and botulinum toxin documented in trials from Johns Hopkins, MD Anderson Cancer Center, and Mount Sinai.
Anatomical variations include accessory slips to the 11th rib or costal cartilage, fusion with psoas major or iliocostalis lumborum, and differing fascial compartmentalization noted in population studies from Tokyo University, Karolinska Institutet, and Universidad Complutense de Madrid. Developmental anomalies and asymmetry have been reported in cadaveric atlases from the Smithsonian Institution and pathological specimens in surgical case series from Guy’s and St Thomas’ NHS Foundation Trust. Such variants may alter biomechanical vectors relevant to spine surgeons at institutions like Mayo Clinic and Queen’s University.
Ultrasound, magnetic resonance imaging (MRI), and computed tomography (CT) are used to assess quadratus lumborum for edema, atrophy, hematoma, or enthesopathy; MRI protocols endorsed by the Radiological Society of North America, American College of Radiology, and European Society of Musculoskeletal Radiology characterize muscle signal changes and fat infiltration. Diagnostic blocks and electromyography (EMG) performed in pain clinics at institutions such as Massachusetts General Hospital and the Cleveland Clinic can localize nociceptive sources and denervation. Imaging guides interventional procedures in vascular and spine centers associated with Johns Hopkins, Karolinska, and University College London.
Rehabilitation strategies include core stabilization, targeted strengthening, fascial mobilization, and proprioceptive training integrated into programs developed by the American College of Sports Medicine, National Strength and Conditioning Association, and physiotherapy curricula at University of Sydney and University of Cape Town. Surgical approaches that traverse or retract the quadratus lumborum—such as retroperitoneal lumbar fusion, nephrectomy, and lateral transpsoas procedures—are described in operative texts from the American Association of Neurological Surgeons, European Spine Journal case series, and technique manuals from the New York Presbyterian/Columbia University practice; consideration of muscle preservation, neurovascular protection, and postoperative rehabilitation is emphasized by enhanced recovery protocols at institutions including ERAS Society centers.
Category:Muscles of the torso