Quadratus Lumborum Anatomy: Origin, Insertion, Action, Innervation

Origin: Transverse processes of L1 to L4, the iliolumbar ligament, and the posterior third of the iliac crest

Insertion: Inferior border of the 12th rib

Actions: Lateral flexion of the lumbar spine

Innervation: Ventral primary rami of T12 to L3

Blood Supply: Branches from the lumbar 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:

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

Note: The intertransversarii assist with lateral flexion of the lumbar spine

1. Elevation of the pelvis when acting unilaterally

Agonists:

Antagonists: None