The iliopsoas muscle is a functionally combined muscle complex consisting of the psoas major and iliacus muscles. Both parts unite in a common tendon that inserts at the lesser trochanter of the femur.
The iliopsoas is the strongest hip flexor of the human body. With the leg fixed, it also bends the trunk forwards. Because it originates at the lumbar vertebral bodies and the iliac fossa, it also influences the position of the lumbar spine and is therefore one of the posture-relevant muscles.