Psoas major (Musculus psoas major)
Educational content only — not medical advice.
Anatomy
The strongest flexor of the hip: from the lumbar vertebrae it passes through the pelvis behind the inguinal ligament to the lesser trochanter — the core muscle of walking, lifting the leg, and coupling trunk to lower limb.
Origin & insertion
Origin: vertebral bodies and discs T12–L5 and their transverse processes. Insertion: lesser trochanter of the femur.
Action
Flexes the hip (with slight lateral rotation) and flexes the trunk from lying down.
Innervation
Direct branches from the lumbar plexus (L1–L3)
Clinical notes
A psoas abscess causes pain and a flexed, externally rotated hip mimicking appendicitis — the psoas sign (resisted hip flexion) is a classic detector.
Related structures
Educational references
FAQ
What is the role of the Psoas major?
The strongest flexor of the hip: from the lumbar vertebrae it passes through the pelvis behind the inguinal ligament to the lesser trochanter — the core muscle of walking, lifting the leg, and coupling trunk to lower limb.
Why is the Psoas major clinically important?
A psoas abscess causes pain and a flexed, externally rotated hip mimicking appendicitis — the psoas sign (resisted hip flexion) is a classic detector.
Source & license
BodyParts3D, © The Database Center for Life Science licensed under CC Attribution 4.0 International (https://creativecommons.org/licenses/by/4.0/). license details