Sacroiliac Joint

Question 1

Sacrum

Answer 1

5 fused vertebrae S1-S5
Wedged shaped
Base: S1
Apex: S5

Question 2

Articulating surfaces: Ala

Answer 2

2 auricular (ear-shaped) surfaces (S1-3)
Multiplanar and corresponds to iliac surfaces
Covered with hyaline cartilage (thicker on sacral surfaces)

Question 3

Base: S1

Answer 3

supports two zygapophyseal facets that face posteriorly for articulation with the inferior facets of the fifth lumbar vertebra

Question 4

Apex: S5

Answer 4

the fifth sacral vertebra, articulates with the coccyx

Question 5

Innominate bone

Answer 5

refers to one side of the pelvis formed by the consolidation of the ilium, ischium, and pubis

Question 6

Innominates

Answer 6

2 ilium: innominates
Each has an auricular articulating surface that corresponds to the sacral articulating surface
Covered with hyaline cartilage (thinners and denser collagen)
Multiplanar (correspond to sacral surfaces)

Question 7

Anterior Structure

Answer 7

Synovial joint

Question 8

Posterior structure

Answer 8

Syndesmosis

Question 9

Role of the SIJ

Answer 9

Relieve the stress on the pelvic ring imparted by movement of the trunk and lower limbs, muscle contractions, the weight of the body, and ground reaction forces

Question 10

Sacroiliac ligament

Answer 10

joints’ stability
strongest ligaments in the body

Question 11

Anterior SI ligament

Answer 11

capsular ligaments

Question 12

Long posterior SI ligament

Answer 12

medial fibers are connected to the deep lamina of the posterior layer of the thoracolumbar fascia and the aponeurosis of the erector spinae

Question 13

Sacrospinous ligament

Answer 13

connect the ischial spines to the lateral borders of the sacrum and coccyx
inferior border of the greater sciatic notch

Question 14

Sacrotuberous ligament

Answer 14

connect the ischial tuberosities to the posterior spines at the ilia and the lateral sacrum and coccyx
inferior border of the lesser sciatic notch

Question 15

Interosseous sacroiliac ligaments

Answer 15

create the more posteriorly located syndesmoses (fibrous union) between the tuberosities of the sacrum and ilia

Question 16

Symphysis Pubis

Answer 16

Cartilaginous joint
Located between the two ends of the pubic bones
Supported by:
superior pubic ligament
inferior pubic ligament
posterior pubic ligament

Question 17

Superior pubic ligament

Answer 17

thick and dense fibrous band that attaches to the pubic crests and tubercles and helps support the superior aspect of the joint

Question 18

Inferior pubic ligament

Answer 18

arches from the inferior rami on one side of the joint to the inferior portion of the rami on the other side and thus reinforces the inferior aspect of the joint

Question 19

Posterior pubic ligament

Answer 19

fibrous membrane that is continuous with the periosteum of the pubic bones

Question 20

Axis of motion: Sacrum

Answer 20

Subclinical amount of motion available
-Rotation and translation
Primary axis to emphasize: Coronal

Question 21

Sagittal Plane

Answer 21

Nutation: movement of the sacrum whereby the sacral base rotates or tips anteriorly on the relatively fixed innominates

Counternutation: the sacral base rotates or tips posteriorly on the relatively fixed innominates

Question 22

Nutation

Answer 22

Sacral base tips/rotates anteriorly (fwd + down)
Sacral “flexion”
Close-packed position

Question 23

Counternutation

Answer 23

Sacral base tips/rotates posteriorly (back +up)
Sacral “extension”
Open-packed position

Question 24

Lumbosacral Flexion

Answer 24

1. Segmental flexion of lumbar vertebrae
2. Sacrum initiates with counternutation while the innominates rotate anteriorly to lock in place
   -Sacrum then shifts to nutation to move w/pelvis as a unit
3. Hip flexion

Question 25

Lumbosacral Extension

Answer 25

1. Segmental extension of lumbar vertebrae
2. Sacrum initiates with nutation while the innominates rotate posteriorly to lock in place
   -Sacrum then shifts to counternutation to move w/pelvis as a unit
3. Hip extension

Question 26

Dynamic Stability: Force Closure

Answer 26

Muscle action/support to stabilize SIJ

Question 27

Form Closure

Answer 27

Describes the stability of the joint from the design of the pelvic anatomy itself