Iliopsoas Muscle: Definition, Location & Function

The iliopsoas is a composite muscle group comprising the iliacus and psoas major muscles.

• Location: Deep in the abdomen and pelvis; originates from the lumbar vertebrae (psoas) and iliac fossa (iliacus), inserts on the lesser trochanter of the femur.
• Innervation: Femoral nerve (L1–L3).
• Primary action: Powerful hip flexion (bringing thigh toward trunk). Also assists in trunk flexion when the femur is fixed.

The iliopsoas is the strongest hip flexor and crucial for walking, running, and posture.