Quadratus Lumborum Anatomy

Quadratus Lumborum Muscle

Origin: Inferior border of the 12th rib
Insertion: Transverse processes of L1 to L4, the iliolumbar ligament, and the posterior third of the iliac crest
Actions: Lateral flexion of the lumbar spine
Innervation: Ventral primary rami of T12 to L3
Blood Supply: Branches from the lumbar artery

Primary Actions of the Quadratus Lumborum

1. Lateral rotation of the lumbar spine when acting unilaterally

  Agonists: 

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

  Antagonists: Same muscles on contralateral side

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

The intertransversarii assist with lateral flexion of the lumbar spine

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Secondary Actions of the Quadratus Lumborum

1. Elevation of the pelvis when acting unilaterally

  Agonists:

  • Rectus abdominis
  • Internal oblique
  • External oblique

  Antagonists:  None