Muscle
Psoas major
Chief hip flexor
High-yield
Directly innervated by ventral rami L1-L3 (not the femoral nerve trunk); psoas sign in appendicitis.
Overview
A long fusiform muscle of the posterior abdominal wall that, with iliacus, forms iliopsoas - the most powerful flexor of the hip.
Reference facts
- Origin
- Transverse processes of L1-L5; bodies of T12-L5 and the intervening intervertebral discs
- Insertion
- Lesser trochanter of the femur (via the iliopsoas tendon)
- Action
- Flexes the thigh at the hip; flexes the trunk; stabilises the lumbar spine
- Innervation
- Anterior rami of L1, L2, L3
- Blood supply
- Lumbar branches / iliolumbar artery
Frequently asked questions
What does the psoas major do?
The psoas major flexes the thigh at the hip; flexes the trunk; stabilises the lumbar spine.
What nerve innervates the psoas major?
The psoas major is innervated by the anterior rami of L1, L2, L3.
Where does the psoas major attach?
The psoas major originates from the transverse processes of L1-L5; bodies of T12-L5 and the intervening intervertebral discs and inserts on the lesser trochanter of the femur (via the iliopsoas tendon).
What is the blood supply of the psoas major?
The psoas major is supplied by the lumbar branches / iliolumbar artery.