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Obliquus internus abdominis



General information

  • This section is strictly limited to anatomy, you might be looking for clinical relevant information which is found under the clinical chapters -- muscles section, click here to go to that page


  • Deep to the obliquus externus
  • Superficial to the transversus abdominis


  • Crista iliaca
  • Inguinal ligamentet
    • Lateral 2/3
  • Thoracolumbar fascia


  • 10-12. ribs
  • Linea alba

Main function

  • Trunk
    • Flexion
    • Lateral flexion
    • Ipsilateral rotation
  • Pelvis
    • Posterior tilt

Secondary function

  • Pelvis
    • Elevation
    • Contralateral rotation
  • Abdominal content
    • Compression

Nerve innervation

  • Segmental
    • Th7-L1

Arterial supply

  • Subcostal and posterior intercostal arteries
  • Deep circumflexion iliac artery
  • Inferior epigastric artery


  • Patient position
    • Supine
  • Place a pillow beneath the patient's knees to gain passive flexion of the hips
  • Have the patient actively rotate the body to the same side (ipsilaterally) while you feel for the contraction

Strength test

  • Patient position
    • Supine
  • Give resistance in a downward and diagonal direction at the medial aspect of the patient's arm
  • The patient generates force in a rotation direction against the resistance