Quadratus lumborum !
The quadratus lumborum is a flat, square muscle deep in the side of the lower back, from the pelvis to the twelfth rib; it bends the trunk sideways.
Official name: Quadratus lumborum muscle
Opens in the Durgical app, no sign-up needed.
What it is
A flat, square muscle deep in the side of the lower back, from the iliac crest to the twelfth rib and the lumbar transverse processes.
What it does
Bends the trunk to the same side, hitches the hip up, steadies the lower back and holds the twelfth rib when you breathe in.
Key facts
- Origin
- Iliolumbar ligament and posterior iliac crest
- Insertion
- Medial half of the inferior border of the 12th rib; transverse processes of L1–L4
- Action
- Lateral flexion of trunk; elevates the hip (hip hike); fixes 12th rib in inspiration; bilateral: extends lumbar spine
- Nerve
- Ventral rami of T12–L4
- Blood supply
- Lumbar, subcostal and iliolumbar arteries
Relations
- In front
- Kidney and colon (ascending on the right, descending on the left), with the subcostal, iliohypogastric and ilioinguinal nerves crossing it; the lateral arcuate ligament above
- Behind
- Erector spinae, separated by the middle layer of the thoracolumbar fascia
- Medial
- Psoas major and the lumbar transverse processes
- Lateral
- Transversus abdominis aponeurosis; its lateral edge borders the superior lumbar triangle (of Grynfeltt) below the 12th rib
- Above
- 12th rib and the lateral arcuate ligament of the diaphragm
- Below
- Iliolumbar ligament and the back of the iliac crest
How to find it
Too deep to see. Lying on the side, it is pressed through the flank just lateral to the erector spinae, between the 12th rib and the iliac crest, and it tightens when the hip on that side is hitched up. On axial CT or MRI it is the flat muscle lateral to psoas major, on the transverse processes.
On imaging
Axial CT or MRI shows it as a flat band beside the lumbar transverse processes, lateral to psoas major and in front of the erector spinae, between the 12th rib and iliac crest. Retroperitoneal haematoma, abscess or tumour can spread into it. Flank ultrasound shows the 'shamrock' view (psoas, erector spinae and quadratus round a transverse process) for the quadratus lumborum block.
Common problems
- Strain or spasm: deep, one-sided low back pain, often worse when standing up or turning in bed.
How it is diagnosed
Exam; imaging only to rule out other causes.
Treatment
- Heat, stretching, strengthening, pain medicine; sometimes trigger point injections.
Clinical notes
- Quadratus lumborum block: under ultrasound, local anaesthetic placed next to it (lateral, posterior or anterior approach) spreads to the nerves of the abdominal wall and, in some approaches, toward the paravertebral space
- A posterior (lumbotomy) approach to the kidney passes along its lateral border
- A superior lumbar hernia (Grynfeltt) can come through the triangle at its lateral edge, below the 12th rib
Related conditions
Test yourself
Think of the answer, then tap the question to see it.
What are the attachments of the quadratus lumborum?
From the iliolumbar ligament and posterior iliac crest to the 12th rib and the transverse processes of L1–L4.
What are the actions of the quadratus lumborum?
Lateral flexion of the trunk, hip hike, fixing the 12th rib in inspiration; bilaterally it extends the lumbar spine.
What nerve supplies the quadratus lumborum?
Ventral rami of T12–L4.
Which nerves cross the anterior surface of the quadratus lumborum?
The subcostal, iliohypogastric and ilioinguinal nerves.
Which hernia can pass through the triangle at the lateral edge of the quadratus lumborum?
A superior lumbar (Grynfeltt) hernia, below the 12th rib.
Educational information, not medical advice. For any symptom, see a health professional.
Its names
- Official Latin (TA2)
- musculus quadratus lumborum TA2 2382
- Official Spanish (DeCS)
- Músculo cuadrado lumbar
- English (TA2)
- Quadratus lumborum muscle
Related
Sources: Terminologia Anatomica (TA2); Anatomy, Abdomen and Pelvis, Quadratus Lumborum.
Spotted a mistake?We are always improving for the community. Tell us what is wrong and our team will review it.Report a mistake
Representative model, for educational purposes only.
