Muscle
Quadratus lumborum
A muscular connection between pelvis, lumbar spine and rib 12
High-yield
The three attachment regions explain its usual actions: lateral bending, lumbar stabilization and fixation of rib 12.
Overview
Quadratus lumborum occupies the posterior abdominal wall beside psoas major. Its fascicles connect the iliac crest, upper lumbar transverse processes and twelfth rib, helping stabilize this junction during trunk movement and breathing.
Reference facts
- Origin
- The iliac crest and iliolumbar ligament provide inferior attachments.
- Insertion
- Superior attachments reach rib 12 and the transverse processes of L1–L4.
- Action
- Assists ipsilateral side-bending; bilateral activity can support lumbar extension. Stabilizing rib 12 helps the diaphragm act during inspiration.
- Innervation
- Anterior rami spanning T12–L4 supply the muscle.
- Blood supply
- Lumbar arteries and the subcostal artery provide arterial branches.
Frequently asked questions
What does the quadratus lumborum do?
Assists ipsilateral side-bending; bilateral activity can support lumbar extension. Stabilizing rib 12 helps the diaphragm act during inspiration.
What nerve innervates the quadratus lumborum?
Anterior rami spanning T12–L4 supply the muscle.
Where does the quadratus lumborum attach?
Origin: The iliac crest and iliolumbar ligament provide inferior attachments. Insertion: Superior attachments reach rib 12 and the transverse processes of L1–L4.
What is the blood supply of the quadratus lumborum?
The quadratus lumborum is supplied by the lumbar arteries and the subcostal artery provide arterial branches.