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 low back vertebrae to the iliac fascia
Illiacus Origin, Insertion, Action, Innervation, Blood Supply
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 Muscle
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.
Psoas Major Origin, Insertion, Action, Innervation, Blood Supply
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 Actions of the Psoas Major Muscle
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 Origin, Insertion, Action, Innervation, Blood Supply
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 Actions of the Psoas Minor Muscle
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.