- Lies in the gutter between bodies and transverse processes of lumbar vertebrae
- Origin:
- Discs above the L5 Lumbar vertebrae (T12 – L5)
- Adjoining vertebral bodies
- Fibrous arches that span the concavities of the sides of the upper 4 vertebral bodies
- Medial ends of all Lumbar Transverse processes
- THUS, one continuous attachment from lower border of T12 to upper border of L5
- Course:
- Downwards along Pelvic Brim
- Passes beneath Inguinal Ligament into Thigh
- Insertion:
- Lesser Trochanter of Femur
- Relations:
- Lumbar plexus embedded within muscle
- Genitofemoral Nerve and Femoral Nerves emerges from the front of the muscle
- Iliohypogastric, Ilioinguinal, Lateral Femoral Cutaneous, emerges from its lateral border
- Obturator Nerve and Lumbosacral Trunk emerge from its medial border
- 4 x Lumbar Arteries and veins pass backwards medial to the 4 arches and run laterally behind the muscle
- External Vertebral Venous Plexus behind it (in front of Transverse Processes)
- Psoas Fascia
- Invests surface of the muscle
- Attached to vertebral bodies, fibrous arches, and transverse processes
- Attached to Iliopubic eminence as muscle extends along pelvic brim
- NOT part of Lumbar Fascia
- Lateral edge blends with the anterior layer of Lumbar Fascia overlying Quadratus Lumborum
- Nerve Supply
- L1, L2 and L3 – mainly L2
- Actions:
- Hip flexion
- Lateral flexion of vertebra
- Flexion of trunk
