Chapter Five: The Lower Limb Gluteal Region

Question 1

skeletal components

Answer 1

• gluteals regions main function is locomotion
• muscles move the thigh in relation to the trunk
• two bones are the hip bone and proximal femur

Question 2

the hip bone

Answer 2

• three bones fused together around the socket of the hip joint (acetabulum)
• three bones are ilium, ischium, pubis

Question 3

ilium

Answer 3

• upper flatter part of the hip bone
• narrowest at the hip joint and flairs upwards to the broad curved iliac crest
• anterior part has a small spinous process (anterior superior iliac spine) (ASIS)
• posterior edge has a homologue (posterior superior iliac spine) (PSIS)
• below is anterior and posterior inferior iliac spines (AIIS, PIIS)

Question 4

ischium

Answer 4

• descends from the ilium to the lowest part of the hip bone (large ischial tuberosity)
• before this there is a sharp backward facing spine of the ischium
• between spine and tuberosity is the smaller lesser sciatic notch
• ischium runs forward from the tuberosity to provide its half

Question 5

pubic bone

Answer 5

• inverted L shaped
• superior pubic ramus runs from the acetabulum horizontally to the body
• two bodies form at the symphysis pubis
• the joint surfaces are large and oval
• inferior ramus runs down and posteriorly to fuse with the ischial component

Question 6

ischium and pubis

Answer 6

• unite at the acetabulum
• pubis is anterior to the ischium
• surround the large foreamen (obturator foreamen)
• obturator membrane covers the foreamen except in a small area at the superior border of the foreamen

Question 7

acetabulum

Answer 7

• inverted horseshoe- shaped articular surface
• provides a secure socket for the head of the femur as it articulates at the hip joint

Question 8

the sacroiliac joints

Answer 8

• joins the sacrum to the two iliac bones, forming the bony pelvis
• joint has two components: synovial joint and fibrous joint

Question 9

synovial joint

Answer 9

• the articular surface of the ilium articulates with the equivalent area on the sacrum
• allows for a little movement to compensate for changes in posture

Question 10

fibrous joint

Answer 10

• is above and posterior to the synovial joint
• fibres run between the tuberosity if the ilium to the back of the sacrum

Question 11

sacrotuberous and sacrospinous ligaments

Answer 11

• two important ligaments from the sacrum to the ischium
• running from the sacrum to the ischial tuberosity and the ischial spine
• function to close off the greater and lesser sciatic notches
• creating the greater and lesser sciatic foramina
• ligaments prevent tilting of the pelvis

Question 12

the proximal femur

Answer 12

• strongest and longest bone in the body
• round shaft with ends for hip and knee joint s
• round head and prominent neck dominate the proximal end
• head articulates with the acetabulum of the pelvis
• where the neck joins the shaft there are two large prominences called the greater and lesser trochanters

Question 13

greater and lesser trochanters

Answer 13

• provide attachment sites for powerful groups of muscles
• greater trochanter is the more lateral of the two

Question 14

intertrochanteric line

Answer 14

• unites the two trochanters anteriorly

Question 15

intertrochanteric crest

Answer 15

• exists posteriorly

Question 16

gluteal tubercle (tuberosity)

Answer 16

• below the greater trochanter on the back of the proximal femur
• rough linear area running downward

Question 17

muscles of the gluteal region

Answer 17

two groups
- the gluteal muscles (3) and tensor fasciate latae
- the lateral rotators (6)

Question 18

gluteal muscles and tensor fasciae latae

Answer 18

• the three gluteal muscles are the gluteus maximus, gluteus medius and gluteus minimus

Question 19

what is the gluteus maximus

Answer 19

• inferior gluteal nerve
• largest of the three and provides roundness of the butt
• powerful, takes origin linearly off the posterior of the ilium, the sacroiliac joint and the sacrotuberous ligament

Question 20

insertion of gluteus maximus

Answer 20

• insertion is complex: the deep third of the muscle inserts on the gluteal tuberosity (direct bone)
• the superficial two thirds of the fibres insert on a band of tissue running down the lateral side of the thigh (the iliotibial band ITB)

Question 21

iliotibial band ITB

Answer 21

• inserts onto the lateral tibial condyle on gerdys tubercle
• part of the deep fascia that surrounds the thigh (the fascia lata)

Question 22

gerdys tubercle

Answer 22

• located on the anterolateral aspect of the proximal tibia

Question 23

gluteus maximus role

Answer 23

• powerful hip extensor, lateral rotator and adductor
• not used in standing or walking but is heavily recruited in climbing and running
• innervated by the inferior gluteal nerve (L5, S1 and S2)

Question 24

gluteus medius

Answer 24

• superior gluteal nerve
• fan shaped muscle originating from the middle of the iliac blade
• running down to a point to insert on the greater trochanter
• medial rotator and abductor
• innervated by the superior gluteal nerve (L4, L5, S1)

Question 25

gluteus minimus

Answer 25

- originate on gluteal surface - deepest and occupies the anterior part of the external surface of the iliac blade - same shape as the medius - inserts on the greater trochanter - gluteus medius and minimus function as one muscle with the same innervation and actions

Question 26

tensor fasciae latae

Answer 26

- arises from the anterior superior iliac spine - runs down several cm and inserts straight into the iliotibial band which in turn inserts onto gerdys tubercle - innervated by the superior gluteal nerve and tenses the ITB - originates from the outer side of the iliac crest

Question 27

lateral rotators: piriformis

Answer 27

- originates inside the pelvis from the front of the sacrum - triangular, passing through the greater sciatic foramen - inserts on the greater trochanter - innervation S1, S2

Question 28

lateral rotators: obturator internus

Answer 28

- obturator internus and two gemelli are one functional unit - obturator internus takes origin from the inside of the obturator membrane - tendon runs through the lesser sciatic foramen, turns 90 degrees and inserts on the greater trochanter

Question 29

lateral rotators: the gemelli

Answer 29

- obturator internus and two gemelli are one functional unit - takes origin from the edge of the foramen one above and one below the obturator internus, with which they insert - innervation L4, L5, S1, S2

Question 30

lateral rotators: obturator externus

Answer 30

- originates from the outside of the obturator membrane and runs laterally to insert on the base of the greater trochanter - innervation L2, L3, L4

Question 31

lateral rotators: quadratus femoris

Answer 31

- square muscle running back from the ischial tuberosity to insert on the middle of the intertrochanteric crest (quadrate tubercle) - innervation L4, L5, S1

Question 32

blood supply and nerves

Answer 32

- superior gluteal nerve, artery and veins enter the region through the greater sciatic foramen overtop of the piriformis - supplies the gluteus medius and minimus - inferior gluteal nerve, artery and veins enter underneath the piriformis - they supply the gluteus maximus and the lower part of the region - huge sciatic nerve runs through the region entering from below the piriforms and running straight down to enter the back of the thigh