Sacrum Region

Question 1

Gluteus Maximus

1. Origin
2. Insertion
3. Action
4. Innervation

Answer 1

Origin:

1. Coccyx
2. Edge of sacrum
3. Posterior iliac crest
4. Sacrotuberous & Sacroiliac ligaments

Insertion:
1. Iliotibial tract (upper fibers)
2. Gluteal tuberosity of the femur (lower fibers)

Action:

All fibers:
1. Extend the hip (coxal joint)
2. Laterally rotate the hip (coxal joint)
3. Abduct the hip (coxal joint)

Lower fibers:
1. Adduct the hip (coxal joint)

Innervation: Inferior gluteal L5, S1, 2

Question 2

Gluteus Medius

1. Origin
2. Insertion
3. Action
4. Innervation

Answer 2

Origin:

1. Gluteal surface of the ilium
2. between posterior and anterior gluteal lines
3. Just below the iliac crest

Insertion:

1. Lateral aspect of the greater trochanter

Action:

All fibers:
Abduct the hip (coxal joint)

Anterior fibers:
Flex the hip (coxal joint)
Medially rotate the hip (coxal joint)

Posterior fibers:
Extend the hip (coxal joint)
Laterally rotate the hip (coxal joint)

Innervation:

Superior gluteal L4, 5, S1

Question 3

Piriformis

1. Origin
2. Insertion
3. Action
4. Innervation

Answer 3

Origin:

1. Anterior surface of the sacrum

Insertion:

1. Superior aspect of the greater trochanter

Action:

1. Laterally rotate the hip (coxal joint)
2. Abduct the hip when the hip is flexed.

Innervation:

Sacral plexus L5, S1, S2

Question 4

Psoas Major

1. Origin
2. Insertion
3. Action
4. Innervation

Answer 4

Origin:

1. Bodies and transverse processes of the lumbar vertebrae

Insertion:

1. Lesser trochanter

Action:

With the origin fixed:
1. Flex the hip (coxal joint)
2. May laterally rotate the hip (coxal joint)

With the insertion fixed:
1. Flex the trunk toward the thigh
2. Tilt pelvis anteriorly

Unilaterally:
Assist to laterally flex the lumbar spine

Innervation:

Lumbar plexus L1, L2, L3, L4

Question 5

Tensor Fasciae Latae

1. Origin
2. Insertion
3. Action
4. Innervation

Answer 5

Origin:

1. Iliac crest, (posterior to the ASIS)

Insertion:

1. Iliotibial tract

Action:

1. Flex the hip (coxal joint)
2. Medially rotate the hip (coxal joint)
3. Abduct the hip (coxal joint)

Innervation:

Superior gluteal L4, L5, S1