Psoas Major

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.

By TeachMeSeries Ltd (2025)

Fig 1
Muscles of the posterior abdominal wall.