Lumbar and SI Muscles (OIAI)

Multifidus origin

Posterior sacrum, PSIS, & thoracic transverse processes

Multifidus insertion

spinous processes 2-4 segments superior to origin

multifidus action

trunk extension and contralateral rotation

multifidus innervation

dorsal rami of spinal nerves

multifidus

n

Quadratus Lumborum origin

Posterior iliac crest, iliolumbar ligament

quadratus lumborum insertion

12th rib, transverse processes L1-4

quadratus lumborum action

Ipsilateral lateral flexion and pelvic elevation

quadratus lumborum innervation

ventral rami T12-L4

quadratus lumborum

n

external oblique origin

External surfaces of ribs 5-12

external oblique insertion

iliac crest and linea alba

external oblique action

contralateral rotation and trunk flexion

external and internal oblique innervation

intercostal nerves

external oblique

n

internal oblique origin

thoracolumbar fascia, iliac crest, inguinal ligament

internal oblique insertion

linea alba, pubic crest, costal cartilages ribs 10-12

internal oblique action

ipsilateral rotation and trunk flexion

internal oblique

n

transverse abdominis origin

inguinal ligament, iliac crest, thoracolumbar fascia and ribs 7-12

transverse abdominis insertion

linea alba and pubic crest

transverse abdominis action

compress and support abdominal viscera

transverse abdominis innervation

intercostal nerves

transverse abdominis

n

rectus abdominis origin

pubic crest and symphysis

rectus abdominis insertion

xiphoid process and costal cartilages of ribs 5-7

rectus abdominis action

trunk flexion, posterior pelvic tilt

rectus abdominis innervation

intercostal nerves

rectus abdominis

n

gluteus maximus origin

posterior ilium, sacrum, coccyx

gluteus maximus insertion

gluteal tuberosity of femur and iliotibial tract

gluteus maximus action

hip extension and external rotation

gluteus maximus innervation

inferior gluteal nerve

gluteus maximus

n

gluteus medius origin

External surface of ilium between anterior and posterior gluteal lines

gluteus medius insertion

greater trochanter of femur

gluteus medius action

Hip abduction, internal rotation, pelvic stabilization

gluteus medius innervation

superior gluteal nerve

gluteus medius

n

iliopsoas origin

transverse processes T12-L5 and Iliac fossa

iliopsoas insertion

lesser trochanter of femur

iliopsoas action

Hip flexion and trunk flexion

iliopsoas innervation

femoral nerve

iliopsoas

n

biceps femoris origin

long head: ischial tuberosity

short head: linea aspera

biceps femoris insertion

head of fibula

biceps femoris action

Knee flexion, hip extension, external rotation

biceps femoris innervation

sciatic nerve

biceps femoris

n

semimembranosus origin

ischial tuberosity

semimembranosus insertion

posterior surface of medial condyle of tibia

semimembranosus and semitendinosus action

knee flexion, hip extension, and hip internal rotation

semimembranosus and semitendinosus innervation

tibial division of sciatic nerve

semimembranosus

n

semitendinosus origin

ischial tuberosity

semitendinosus insertion

pes anserine

semitendinosus

n

rectus femoris origin

AIIS and superior margin of acetabulum

rectus femoris insertion

tibial tuberosity via patellar ligament

rectus femoris action

hip flexion, knee extension

rectus femoris innervation

femoral nerve

rectus femoris

n

piriformis origin

anterior surface of sacrum

piriformis insertion

Superior border of greater trochanter of femur

piriformis action

external rotation and hip abduction

piriformis innervation

nerve to piriformis

piriformis

n