Iliopsoas Muscle Anatomy

Iliopsoas Muscles

The iliopsoas is a group of three individual muscles:

  • The iliacus that lines the ilium
  • The psoas major that connects the lower back vertebrae to the femur
  • The psoas minor that connects the the low back vertebrae to the iliac fascia

Iliacus Muscle

The Iliacus Muscle

Origin: Superior two-thirds of the internal surface of the iliac fossa, the inner lip of the iliac crest, the ventral surface of the sacroiliac and iliolumbar ligaments, and the upper surface of the lateral part of the sacrum
Insertion: The lesser trochanter of the femur after being joined by the tendon of psoas major
Actions: Flexion of thigh at the hip
Innervation: Femoral nerve (L2, L3)
Blood Supply: Iliolumber artery from the internal iliac artery

Primary Actions of the Iliacus

1.  Flexion of thigh at the hip

Agonists:

  • Psoas Major

Antagonists:

  • Gluteus maximus
  • Semitendinosus
  • Semimembranosus
  • Biceps Femoris (long head)
  • Adductor magnus (posterior part)

Note: Pectineus, rectus femoris, sartorius, and psoas minor assist with flexion of the thigh at the hip.

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Psoas Major Muscle

Psoas Major Muscle

Origin: Anterior surfaces of the vertebral bodies, intervertebral discs and transverse processes of T12-L5 vertebrae
Insertion: The lesser trochanter of the femur after being joined by the tendon of the iliacus
Actions: Flexion of thigh at the hip
Innervation: Lumbar plexus (L2, L3,  L4)
Blood Supply: Iliolumber artery from internal iliac artery

Primary Action of the Psoas Major:

1.  Flexion of thigh at the hip

  Agonists:

  • Iliacus

  Antagonists:

  • Gluteus maximus
  • Semitendinosus
  • Semimembranosus
  • Biceps Femoris (long head)
  • Adductor magnus (posterior part)

Note: Pectineus, rectus femoris, sartorius, and psoas minor assist with flexion of the thigh at the hip.

Secondary Actions of the Psoas Major Muscle

1.  Assists with extension of the lumbar spine

  Agonists:

  • Iliocostalis lumborum
  • Longissimus thoracis

  Antagonists:

  • Rectus Abdominis

Note: Interspinalis also assist with extension of the lumbar spine

Psoas Minor Muscle

Psoas Minor Muscle

Origin: Bodies of T12 and L1 and intervening intervertebral discs
Insertion: Attaches to the pectineal line, the iliopectineal eminence and the iliac fascia
Actions: Flexion of thigh at the hip
Innervation: Ventral primary rami of L1
Blood Supply: Iliolumber artery from internal iliac artery

Primary Action of the Psoas Minor:

Because of its position and size the psoas minor is not a prime mover

Secondary Actions of the Psoas Minor Muscle

1.  Assists with flexion of the thigh at the hip

  Agonists:

  • Psoas Major
  • Iliacus

  Antagonists:

  • Gluteus maximus
  • Semitendinosus
  • Semimembranosus
  • Biceps Femoris (long head)
  • Adductor magnus (posterior part)

Note: Pectineus, rectus femoris, sartorius, and psoas minor assist with flexion of the thigh at the hip.

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