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Quadratus Lumborum: Origin, Insertion, Action, Innervation

Quadratus Lumborum muscle location diagram

Table of Contents

Quadratus Lumborum Origin, Insertion, Action
Primary Actions of the Quadratus Lumborum
Secondary Actions of the Quadratus Lumborum

Origin: Posterior third of the iliac crest, the iliolumbar ligament

Insertion: Inferior border of the 12th rib, transverse processes of the L1-L4 vertebrae

Actions: Extension and lateral flexion of the lumbar spine

Innervation: Ventral primary rami of T12 to L3

Blood Supply: Branches from the lumbar artery, subcostal artery, iliolumbar artery

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Primary Actions of the Quadratus Lumborum

1. Lateral flexion of the lumbar spine when acting unilaterally

Agonists: 

    • Iliocostalis lumborum
    • Longissimus thoracis
    • Psoas major
    • External oblique
    • Internal oblique

  Antagonists:

The same muscles on the opposite side

    • Iliocostalis lumborum
    • Longissimus thoracis
    • Psoas major
    • External oblique
    • Internal oblique

1. Extension of the spine 

Agonists: 

    • Erector spinae muscles
    • Multifidus

  Antagonists:

    • Rectus Abdominis

Secondary Actions of the Quadratus Lumborum

1. Elevation of the pelvis when acting unilaterally

Agonists:

    • Rectus abdominis
    • Internal oblique
    • External oblique

Antagonists: 

    • Gluteus medius
    • Gluteus minimus