Pelvis/SIJ Anatomy, Biomechanics & Definitions

Question 1

Which supporting ligament of the SI joint is the weakest?

Answer 1

-ventral (anterior sacroiliac)

Question 2

Which supporting ligament of the SI joint is the strongest?

Answer 2

-interosseous

Question 3

anterior SIJ neurology

Answer 3

-ventral rami of L3-S1

Question 4

posterior SIJ neurology

Answer 4

-posterior rami of L4-S2

Question 5

sacroiliac motion

Answer 5

-movement of sacrum on the ilium

Question 6

How is sacral motion described?

Answer 6

-by the way the anterior surface is facing

Question 7

sacral nutation

Answer 7

• flexion
• relative movement of anterior tilt of the top of the sacrum on the ilium
• occurs during exhalation

Question 8

sacral counternutation

Answer 8

• extension
• relative posterior tilt of the top of the sacrum on the ilium
• occurs during inhalation

Question 9

anterior ilial rotation

Answer 9

-ASIS & pubis roll down, ischial tuberosity moves posterior & PSIS superiorly

Question 10

posterior ilial rotation

Answer 10

-superior ilium rocks backwards & ASIS & pubis roll up, the ischial tuberosity moves anterior & the PSIS moves inferiorly

Question 11

transverse plane osteokinematics of sacrum

Answer 11

• rotation (torsion)
• named by the direction the sacrum rotates TOWARD
• the unilateral movement of the sacral base occurs in transverse plane around an oblique axis

Question 12

relationship of sacrum & innominate during sacral nutation

Answer 12

-innominate posteriorly rotates

Question 13

relationship of sacrum & innominate during sacral counternutation

Answer 13

-innominate anteriorly rotates

Question 14

How do the innominates rotate during trunk forward bending?

Answer 14

-rotate anteriorly

Question 15

How do the innominates rotate during trunk backward bending?

Answer 15

-posteriorly

Question 16

Incidence (in percent) of Pelvis/SIJ dysfunction

Answer 16

-15% of all complaints of lower back pain

Question 17

What kind of diagnostic imaging is considered to be the “gold standard” of diagnosis for SIJ pathology?

Answer 17

-SIJ fluoroscopic blocks

Question 18

Function of Pelvis/SIJ

Answer 18

1. transfer load from trunk to legs during gait as well as during upright movements
2. absorb LE motion before reaching lumbar spine
3. stability

Question 19

Innominate bilateral anterior rotation occurs during what trunk motion?

Answer 19

Trunk flexion

Question 20

Innominate bilateral posterior rotation occurs during what trunk motion?

Answer 20

Trunk extension

Question 21

Innominate unilateral anterior rotation occurs during which motion happening in the LEs?

Answer 21

LE extension

Question 22

Innominate unilateral posterior rotation occurs during which motion at the LEs?

Answer 22

LE flexion

Question 23

Iliosacral disorder: anterior rotation definition & how it presents itself

Answer 23

Superior ilium rocks forward, ASIS & pubis roll down, ischial tuberosity moves posterior & the PSIS superiorly

Question 24

Iliosacral disorder: posterior rotation definition and how it presents itself

Answer 24

Superior ilium rocks backwards & the ASIS & pubis roll up, the ischial tuberosity moves anterior & the PSIS moves inferiorly

Question 25

Inflare

Answer 25

ASIS is relatively more medial compared to unaffected side & PSIS is more lateral. A normal motion during hip internal rotation

Question 26

Outflare

Answer 26

ASIS is relatively more lateral compared to unaffected side & PSIS is more medial. Occurs normally during hip external rotation

Question 27

Upslip

Answer 27

One side of the pelvic girdle is up compared to the opposite side & can occur from a sudden step down, like missing a curb with the knee extended. -appears more commonly than sow slip

Question 28

Downslip

Answer 28

Rare occurrence due to trauma such as being pulled by the LE and is defined as one side of the pelvic girdle being down compared to the opposite side

Question 29

Which plane and around which axis do downslips and upslips occur?

Answer 29

In the frontal plane around a sagittal axis

Question 30

Sacral bilateral flexion occurs during what movements/motions?

Answer 30

Supine to stand; initial stages of trunk flexion

Question 31

Sacral bilateral extension occurs during what movements/motions?

Answer 31

Supine lying; sometimes at the end of trunk flexion

Question 32

Sacral unilateral flexion occurs during what motion?

Answer 32

Flexion of LE

Question 33

Sacral unilateral extension occurs during what motion?

Answer 33

Extension of LE

Question 34

Anterior sacral torsion - left side

Answer 34

(Left oblique axis) as sacrum rotates left on the axis, the upper right corner of the sacrum moves anterior into the body. This makes the right sacral sulcus more prominent (deeper)

Question 35

Sacral anterior torsion - right

Answer 35

(Right oblique axis) as sacrum rotates to the right on the axis, the upper left corner of the sacrum moves into the body. This might make the left sacral sulcus more prominent (deeper)