Psoas Major

Written by Aren Mnatzakanian

Last updated January 5, 2023 • 5 Revisions •

The psoas major is a muscle of the posterior abdominal wall. It is a long, thick muscle located immediately lateral to the lumbar vertebrae. It combines with the iliacus muscle to form the iliopsoas – the major flexor of the thigh at the hip joint.

  • Attachments: Originates from the transverse processes and vertebral bodies of T12 – L5. It then moves inferiorly and laterally, running deep to the inguinal ligament, and attaching to the lesser trochanter of the femur.
  • Actions: Flexion of the thigh at the hip and lateral flexion of the vertebral column.
  • Innervation: Anterior rami of L1 – L3 nerves.
  • Blood supply: Lumbar branch of iliolumbar artery.

Fig 1
Muscles of the posterior abdominal wall.

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