Lumbar Spine Muscles

Question 1

Abdominal muscles:
External Oblique:
O: external surfaces of ribs 5-12
I: linea alba, pubic tubercle, anterior half of iliac crest
A: bilateral: flexion
A: unilateral: lateral flexion, and contralateral rotation of trunk, compression & stabilization of the abdomen
N: intercostal nerves (T7-T1, may include T5, T6, T12) - Ventral rami

Answer 1

Muscle Testing: Upper Abdominals:

Patient: supine, legs extended,
Fixation: none
Test: slow trunk curl
Pressure/resistance: weight of upper body

Question 2

Abdominal muscles:
Internal Oblique:
O: anterior & middle ⅓’s of the iliac crest, lateral ⅔’s of inguinal ligament
I: inferior borders of ribs 10-12, linea alba, and the crest of the pubis
A: bilateral: flexion
A: unilaterally: lateral flexion and ipsilateral rotation of the trunk, compression & stabilization of the abdomen, depress thorax-assists in respiration
N: intercostal nerves (T7-L1)- Ventral rami

Answer 2

Muscle Testing: Upper Abdominals:

Patient: supine, legs extended,
Fixation: none
Test: slow trunk curl
Pressure/resistance: weight of upper body

Question 3

Abdominal muscles:
Transversus Abdominis:
O: internal surfaces of costal cartilages 7-12 mixing with the diaphragm, thoracolumbar fascia, anterior ¾ of the iliac crest, lateral 1/3 inguinal ligament
I: linea alba with abdominal aponeurosis (rectus sheath), pubic crest and the pectineal line (pecten pubis)
A: acts like a girdle, compression and stabilization of the abdomen
N: Intercostal nerves (T7-L1) and Iliohypogastric & Ilioinguinal nerves

Question 4

Abdominal muscles:
Rectus Abdominis:
O: pubic crest & pubic symphysis
I: costal cartilage of ribs 5-7 & xiphoid process
A: flexion of trunk, posterior pelvic tilt, compression and stabilization of the abdomen
N: intercostal nerves (T5-T12) – ventral rami

Answer 4

Upper Abdominals
Patient: supine, legs extended,
Fixation: none
Test: slow trunk curl
Pressure/resistance: weight of upper body

Question 5

Pyramidalis:
O: pubic crest
I: linea alba
A: tenses the linea alba
N: Subcostal Nerve (12th intercostal nerve)

** is absent in ~20% of the population
Linea Alba: fibrous structure that runs down the middle of the abdomen

Question 6

Psoas Major:
O: ventral surfaces of the transverse processes of all lumbar vertebrae, sides of the bodies & corresponding discs of the last thoracic and all lumbar vertebrae,
I: lesser trochanter of femur
A: flexion & lateral rotation of hip; flexion & lateral flexion of spinal joints; anterior pelvic tilt
N: lumbar plexus (L1, 2, 3, 4)

Answer 6

Muscle Testing: Iliopsoas:

Patient: supine
Fixation: examiner stabilizes opposite iliac crest
Test: hip flexion in slight abduction and slight lateral rotation
Pressure/resistance: against the anteromedial aspect of the leg

Question 7

Psoas Minor:
O: sides of the bodies of the T12 & L1 vertebrae, and the disc in between them
I: iliopectineal eminence, arcuate line of the ilium & iliac fascia
A: flexion of the pelvis on the lumbar spine
N: Lumbar plexus (L1, 2)

**Psoas minor muscle is absent in ~50% of people

Question 8

Iliacus:
O: superior 2/3 of the iliac fossa, internal lip of the iliac crest, iliolumbar & sacroiliac ligaments, and the ala of the sacrum
I: lateral side of the tendon of the psoas major & distal to the lesser trochanter
A: flexion & lateral rotation of hip joint; anterior pelvic tilt
N: femoral nerve (L1, 2, 3, 4)

Answer 8

Iliopsoas:
Patient: supine
Fixation: examiner stabilizes opposite iliac crest
Test: hip flexion in slight abduction and slight lateral rotation
Pressure/resistance: against the anteromedial aspect of the leg