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 and bodies of vertebrae T12–L5 and intervening 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