The iliopsoas muscle (also called iliopsoas, latin: musculus iliopsoas) consists of two muscles, the psoas major and iliacus muscles, which have different areas of origin but common insertion.
The psoas major originates from the lateral sides of the lumbar vertebrae (I-IV) and intervertebral discs. The iliacus originates from the iliac fossa. The psoas major and iliacus unify at the level of the inguinal ligament becoming the iliopsoas muscle. The iliopsoas muscle inserts at the lesser trochanter of the femur.
The major functions of the iliopsoas are flexion of the hip joint and external rotation of the thigh.