Iliocostalis Lumborum Anatomy

Iliocostalis Lumborum O, I, A

Origin:  The iliolumbar fascia, the posterior medial lip of the iliac crest, the lateral crest of the sacrum, and the spinous processes of T11 to L5
Insertion: Inferior borders of the angles of the lower six or seven ribs
Actions:  Extension and lateral flexion of the thoracic spine, extension and lateral flexion of the lumbar spine
Innervation:  Dorsal primary rami of T11 to L5
Blood Supply: Intercostal and lumbar arteries

Primary Actions of the Iliocostalis Lumborum

1.  Extension of the thoracic spine when acting bilaterally

Agonists:
  • Iliocostalis cervicis
  • Iliocostalis thoracis
  • Longissimus cervicis
  • Longissimus thoracis
  • Spinalis thoracis
  • Semispinalis cervicis
  • Semispinalis thoracis
  Antagonists:
  • Rectus Abdominis
2.  Lateral flexion of the thoracic spine when acting unilaterally

  Agonists:
  • Iliocostalis cervicis
  • Iliocostalis thoracis
  • Longissimus cervicis
  • Longissimus thoracis
  • External Oblique
  • Internal Oblique
  Antagonists: Same muscles on contralateral side
  • Iliocostalis cervicis
  • Iliocostalis thoracis
  • Longissimus cervicis
  • Longissimus thoracis
  • External Oblique
  • Internal Oblique
3. Extension of the lumbar spine when acting bilaterally

  Agonists:
  • Longissimus thoracis
  • Spinalis thoracis
  Antagonists:
  • Rectus Abdominis
4. Lateral flexion of the lumbar spine when acting unilaterally

  Agonists:
  • Longissimus thoracis
  • Psoas major
  • Quadratus lumborum
  • External oblique
  • Internal oblique
Antagonists: Same muscles on contralateral side
  • Longissimus thoracis
  • Psoas major
  • Quadratus lumborum
  • External oblique
  • Internal oblique

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