Functions of Quadratus Lumborum Muscle

Last updated: February 7, 2026Reviewed date: February 7, 2026Reading time: 5 min read
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Article Summary

Functions of Quadratus Lumborum Muscle/Quadratus Lumborum Muscle informally called the QL, is a paired muscle of the left and right posterior abdominal wall. It is the deepest abdominal muscle and commonly referred to as a back muscle. Each is irregular and quadrilateral in shape. The quadratus lumborum muscles originate from the wings of the ileum; their insertions are on the transverse processes of the upper...

Key Takeaways

  • This article explains Origin And Insertion of Quadratus Lumborum Muscle in simple medical language.
  • This article explains Blood Supply of Quadratus Lumborum Muscle in simple medical language.
  • This article explains Nerve Supply /Innervation of Quadratus Lumborum Muscle in simple medical language.
  • This article explains Functions of Quadratus Lumborum Muscle in simple medical language.
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Definition

Functions of Quadratus Lumborum Muscle/Quadratus Lumborum Muscle informally called the QL, is a paired muscle of the left and right posterior abdominal wall. It is the deepest abdominal muscle and commonly referred to as a back muscle. Each is irregular and quadrilateral in shape. The quadratus lumborum muscles originate from the wings of the ; their insertions are on the transverse processes of the upper four plus the lower posterior border of the twelfth rib. Contraction of one of the pair of muscles causes lateral flexion of the , the elevation of the , or both. Contraction of both causes extension of the lumbar spine.

The quadratus lumborum (QL) muscle resides in the deep and posterior, lateral and inferior areas of the spine, involving the iliac crest, the transverse processes of the lumbar vertebrae and the 12th rib. The muscular organization is complex, and it is difficult to identify precisely the actions that occur through the contraction of fibers. It is an integral part of the thoracolumbar . There is still no certainty that an of QL is the primary source of back pain. The QL could potentially act as a crossroad of the forces exerted by the neighboring muscles, influencing the vectors of the different tensions produced. Thanks to its strategic position and the entropic scheme of its fibers, QL is a significant means of access for anesthesia, during surgery on the back, lower limbs or abdominal area. The article reviews the latest anatomical and information on the quadratus lumborum.

Functions of Quadratus Lumborum Muscle

Attachments

  • The medial half of inferior margins of 12th ribs and upper four lumbar transverse processes. Iliac Crest (specifically the top and back part of the pelvis) The bone at the top and back of the pelvis is known as the .
  • Transverse processes (bony parts that stick out to the side of each ) of lumbar vertebrae usually just the top four lumbar vertebrae
  • The 12th rib (That’s the last rib, also known as a floating rib because it does not attach to the )
  • Origin – medial half of inferior margins of 12th ribs and upper four lumbar transverse processes. It starts from the iliac crest of the ilium and runs craniomedially, attaching to the 12th rib and the transverse processes of the 1st to 5th lumbar vertebrae. All fibers together give the muscle a rectangular appearance.
  • Location – dorsal abdominal wall
  • Insertion – iliolumbar  and internal rim of the iliac crest

Relation

  • The muscle is a thick, irregular, quadrilateral-shaped muscle sheet that lies in the posterior abdominal wall. Thick, irregular, quadrilateral-shaped muscle sheet that lies in the posterior abdominal wall with related to,
  • The quadratus lumborum fills a great amount of space within the and is therefore in close proximity to many structures. The , the , and the  are located ventrally to the muscle, whereas the intrinsic back muscles lie dorsomedially. Both the iliohypogastric and ilioinguinal nerves course on the ventral surface of the quadratus lumborum after exiting the lumbar plexus and continue towards the lateral abdominal muscles.


The quadratus lumborum muscle is supplied by

  • Branches of the lumbar
  • Other smaller arterial branches, as described below
  • Branches of the lumbar
  • The arteria lumbalis ima
  • The lumbar branch of the iliolumbar artery
  • Branches of the subcostal artery
  • Anterior branches of the ventral rami of T12 to L4.
  • Ventral rami of the 12th nerve
  • L1-L4 spinal nerves

Functions of Quadratus Lumborum Muscle

The quadratus lumborum can perform four actions:

  • Extension and lateral flexion of the vertebral column; fixes 12th rib during inspiration to stabilize the diaphragm
  • To bring the ribs closer to the pelvis on the same side, known as lateral flexion
  • It’s often referred to as the “hip hiker” as it can lift the pelvis toward the lower ribs on the same side.
  • Lateral flexion of the vertebral column, with ipsilateral contraction
  • Extension of the lumbar vertebral column, with contraction (based on a line of force passing ~3.5 cm posterior L3 rotation axis[rx])
  • Fixes the 12th rib during forced expiration. The quadratus lumborum assists the diaphragm in inhalation
  • Elevates the Ilium (bone), with ipsilateral contraction (“hip hiking”)

Additional functions

  • Vertical stabilization of pelvis, lumbar spine, and lumbosacral junction. Prevents collapse of the vertebral column in the frontal plane (i.e. scoliosis)
  • Reserve mover actions: Anterior pelvic tilt. Contralateral lateral pelvic rotation.

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 the vertebral column
  • When both sides contract, extends the lumbar spine.


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Which doctor may help?

Start with a registered doctor or the nearest qualified health center.

What to tell the doctor

  • Write when the problem started and how it changed.
  • Bring old prescriptions, investigation reports, and current medicines.
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  • Bring one family member if the patient is weak, elderly, confused, or a child.

Questions to ask

  • What is the most likely cause of my symptoms?
  • Which danger signs mean I should go to hospital quickly?
  • Which tests are necessary now, and which can wait?
  • How should I take medicines safely and what side effects should I watch for?
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Tests to discuss

  • Vital signs: temperature, pulse, blood pressure, oxygen saturation
  • Basic physical examination by a clinician
  • CBC, urine test, blood sugar, or imaging only when clinically needed

Avoid these mistakes

  • Do not use antibiotics, steroid tablets/injections, or strong painkillers without proper medical advice.
  • Do not hide pregnancy, kidney disease, ulcer, allergy, or blood thinner use.
  • Do not delay emergency care when danger signs are present.

Medicine safety and first-aid guide

This section is for patient education only. It does not replace a doctor, pharmacist, or emergency care.

Safe first steps

  • Avoid heavy lifting, sudden bending, and prolonged bed rest.
  • Use comfortable posture and gentle movement as tolerated.
  • Discuss physiotherapy, X-ray, or MRI only when clinically needed.

OTC medicine safety

  • For mild back pain, pain-relief medicine may be discussed with a doctor or pharmacist.
  • Avoid repeated painkiller use if you have kidney disease, stomach ulcer, uncontrolled blood pressure, or are taking blood thinners.

Avoid these mistakes

  • Do not start antibiotics without a proper medical decision.
  • Do not use steroid tablets or injections casually for quick relief.
  • Do not delay emergency care because of home remedies.

Get urgent help if

  • Back pain with leg weakness, numbness around private area, loss of urine/stool control, fever, cancer history, or major injury needs urgent care.
Medicine names, dose, and timing must be decided by a qualified clinician or pharmacist after checking age, pregnancy, allergy, other diseases, and current medicines.

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Write your symptoms, medicines already taken, test results, and questions before visiting a doctor. This note stays on your device unless you print or copy it.

Doctor to discuss: Orthopedic / spine specialist, physical medicine doctor, or qualified clinician
Tests to discuss with doctor
  • Neurological examination for leg power, sensation, reflexes, and straight leg raise
  • X-ray only if injury, deformity, long-lasting pain, or doctor suspects bone problem
  • MRI discussion if severe nerve symptoms, weakness, bladder/bowel problem, or persistent symptoms
Questions to ask
  • What is the most likely cause of my symptoms?
  • Which warning signs mean I should go to emergency care?
  • Which tests are really needed now?
  • Which medicines are safe for my age, pregnancy status, allergy, kidney/liver/stomach condition, and current medicines?
  • Is physiotherapy, posture correction, or activity modification needed?

Emergency warning signs such as chest pain, severe breathing difficulty, sudden weakness, confusion, severe dehydration, major injury, or loss of bladder/bowel control need urgent medical care. Do not wait for online information.

Safe pathway to proper treatment

Care roadmap for: Functions of Quadratus Lumborum Muscle

Use this simple roadmap to understand the next safe steps. It is educational and does not replace examination by a doctor.

Go to emergency care if you notice:
  • Severe or rapidly worsening symptoms
  • Breathing difficulty, chest pain, fainting, confusion, severe weakness, major injury, or severe dehydration
Doctor / service to discuss: Qualified healthcare provider; specialist depends on symptoms and examination.
  1. Step 1

    Check danger signs first

    If danger signs are present, seek emergency care and do not wait for online information.

  2. Step 2

    Record the symptom story

    Write when symptoms started, severity, medicines already taken, allergies, pregnancy status, and test results.

  3. Step 3

    Visit a qualified clinician

    A doctor, nurse, or qualified healthcare provider can examine you and decide which tests or treatment are needed.

  4. Step 4

    Do only useful tests

    Do tests after clinical assessment. Avoid unnecessary tests, random antibiotics, or repeated medicines without diagnosis.

  5. Step 5

    Follow up and return early if worse

    If symptoms worsen, new warning signs appear, or treatment is not helping, return for review quickly.

Rural patient practical tips
  • Take a written symptom diary and all previous prescriptions/test reports.
  • Do not hide medicines already taken, even herbal or over-the-counter medicines.
  • Ask which warning signs mean urgent referral to hospital.

This roadmap is for education. A real diagnosis and treatment plan requires history, examination, and clinical judgment.