Iliopsoas Muscles

The iliopsoas muscle is frequently regarded as a single muscle, because it is a blending of two muscles, the psoas major and the iliacus. The "psoas major" is a powerful flexor muscle of the thigh at the hip joint. If both psoas major muscles are fixed from below, they act as important flexors of the trunk on the hip, as in sitting up from a lying-down position. The "psoas minor" is a weak flexor of the trunk and the lumbar spinal column. It is supplied by a branch of the first lumbar nerve. The "iliacus" works with the psoas major as a powerful flexor of the thigh at the hip joint. It joins the psoas in a number of other actions as the "iliopsoas."