abdominal/lower limb muscle

1. PSOAS MAJOR
Dr M Idris Siddiqui
The long, thick, fusiform psoas
major lies lateral to the lumbar
vertebrae

4. The psoas fascia
• The psoas fascia covering the psoas major (psoas
sheath) is attached medially to the lumbar
vertebrae and pelvic brim .
• The psoas fascia (sheath) is thickened superiorly
to form the medial arcuate ligament.
• The psoas fascia fuses laterally with the quadratus
lumborum and thoracolumbar fascias.
• Inferior to the iliac crest, the psoas fascia is
continuous with the part of the iliac fascia covering
the iliacus. The psoas fascia also blends with the
fascia covering the quadratus lumborum.

5. Four parts
a) Thoracic part( lies in posterior mediastinum)lies bhind
medial arcuate ligament. It may be related to pleura.
b) Abdominal part:
• Upper part forms part of posterior abdominal Wall.
• Intermediate part crosses sacroiliac joint & runs along
true pelvic brim.
• Lower part passes behind inguinal ligament.
c)Pelvic part
d)Femoral part lies in front of hip joint from which it is
separated by a big bursa.

8. Relations of abdominal Part
Anteriorly related to kidney, renal vessels( at L1), ureters,
gonadal vessels, genitofemoral nerve
Medially related to sympathetic trunk, lumbar vessels,(lie between
tendinious arches & vertebral bodies, IVC on right side &
aorta on left side.
Laterally emerge iliohypogastric, ilioinguinal, lateral femoral
cutaneous & femoral Nerves. It is overlapped by quadratus
lumborum
Posteriorly related to
1) transverse processes of lumbar vertebrae
2) medial edge of quadratus lumborum,
3) lumbar plexus lies in substance of muscle,
4) external vertebral venous plexus ( lies in front
of tranverse processes)

10. Relations of pelvic part
Anteriorly: External iliac artery, gonadal
vessels, genjitofemoral nerve
Laterally: Femoral nerve
• Left psoas is crossed by terminal part of
descending colon
• Right psoas is crossed by terminal part of
ilium

13. Relations of femoral part
• Lies inferior to inguinal
ligament, in front of hip joint
(separated by a bursa), iliacus
is lateral to it, pectius is medial,
• Femoral artery lies in front of
muscle

14. Relations of lumbar plexus to psoas
• The genitofemoral nerve emerges through its
anterior surface.
• The obturator nerve & emerge at its
• The lumbosacral trunk medial border
• The iliohypogastric nerve emerge
• The ilioinguinal nerve at its
• The lateral cutaneous nerve of thigh lateral
• The femoral nerve border

15. Psoas Fascia and Tuberculosis
• The psoas fascia covers the anterior surface of
the psoas muscle and can influence the
direction taken by a tuberculous abscess.
• Tuberculous disease of the thoracolumbar
region of the vertebral column results in the
destruction of the vertebral bodies, with
possible extension of pus laterally under the
psoas fascia. From there, the pus tracks
downward, following the course of the psoas
muscle, and appears as a swelling in the upper
part of the thigh below the inguinal ligament.
• It may be mistaken for a femoral hernia.

17. Iliopsoas test
• The iliopsoas has extensive and clinically important
relations to the kidneys, ureters, cecum, appendix,
sigmoid colon, pancreas, lumbar lymph nodes, and
nerves of the posterior abdominal wall. When any of
these structures is diseased, movement of the
iliopsoas usually causes pain.
• The person is asked to lie on the unaffected side and
to extend the thigh on the affected side against the
resistance of the examiner's hand. The elicitation of
pain with this maneuver is a positive psoas sign.
• An acutely inflamed appendix, for example, will produce a
positive right psoas sign. Because the psoas lies along the
vertebral column and the iliacus crosses the sacroiliac joint,
disease of the intervertebral and sacroiliac joints may cause
spasm of the iliopsoas, a protective reflex.