Iliopsoas muscle

Origin: Iliac fossa (iliacus, sacrum (iliacus), spine (T12, L1, L2, L3, L4, L5) and intervertebral discs (psoas major, psoas minor)

Insertion: Femur: lesser trochanter (psoas major/minor), shaft below lesser trochanter (iliacus), tendon of psoas major and femur (iliacus)

Artery: Medial femoral circumflex artery, iliolumbar artery

Nerve: Femoral nerve, Lumbar nerves L1, L2

Action: Flexion of hip (psoas major/minor, iliacus), spine rotation (psoas major/minor)

Antagonist: Gluteus maximus, posterior compartment of thigh

Description:
The term iliopsoas refers to the combination of the psoas major and the iliacus at their inferior ends. These muscles are distinct in the abdomen, but usually indistinguishable in the thigh. As such, they are usually given the common name andquot;iliopsoasandquot; and are referred to as the andquot;dorsal hip musclesandquot; or andquot;inner hip musclesandquot;. The psoas minor does not contribute to the iliopsoas muscle.
Actions.—The Psoas major, acting from above, flexes the thigh upon the pelvis, being assisted by the Iliacus; acting from below, with the femur fixed, it bends the lumbar portion of the vertebral column forward and to its own side, and then, in conjunction with the Iliacus, tilts the pelvis forward. When the muscles of both sides are acting from below, they serve to maintain the erect posture by supporting the vertebral column and pelvis upon the femora, or in continued action bend the trunk and pelvis forward, as in raising the trunk from the recumbent posture.