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Psoas major



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
  • The muscle unites with the iliacus to become the iliopsoas


  • Deep


  • Along the lateral side of the lumbar vertebral bodies of Th12-L5 as well as the accompanying intervertebral discs
  • Procesus transversus L1-L5
    • Anterior aspect


  • Trochanter minor femur

Main function

  • Hip
    • Flexion
    • Lateral rotation
  • Trunk
    • Flexion
    • Lateral flexion
  • Pelvis
    • Anterior tilt

Secondary function

  • Trunk
    • Contralateral rotation
  • Pelvis
    • Contralateral rotation

Nerve innervation

  • Segmental
    • L1-L4
  • Peripheral
    • Plexus lumbalis

Arterial supply

  • Lumbar artery
  • Iliolumbar artery

Palpation muscle belly

  • Patient position
    • Supine
  • Place the patient's hips in flexion by placing a pillow under the knees
  • Place your hand on the patient's stomach between crista iliaca and the 12th rib about halway between SIAS and umbilicus
  • Palpate deep with even pressure towards psoas major in a posteromedial direction

Strength test

  • Patient position
    • Supine
  • Stabilize the opposite crista iliaca with your hand
  • Ask the patient to hold the knee extended throughout the testing
  • Position the patient's hip in flexion and somewhat abduction and lateral rotation
  • Give resistance towards the anteromedial aspect of the lower tibia in an extension and somewhat abduction direction so that the patient is giving force towards flexion and adduction