Functional Anatomy and Biomechanics of the Pelvis

Question 1

There are 2 joints in the pelvis. Name and describe them.

Answer 1

1. Lumbosacral joint at L5-S1.
2. Pubic symphysis, a fibrocartilagenous joint that is critical for stability.
3. Ilio-sacral joint, part synovial (sacrum), part fibrocartilagneous (ilia); L shape joint

Question 2

In the ilio-sacral joint, which cartilage is thicker: hyaline articular of the sacrum, or fibrocartilage of the ili?

Answer 2

Sacral cartilage.

Question 3

Where is the axis of motion for nutation / counter-nutation in the pevlis?

Answer 3

S2 @ PSIS

Question 4

In terms of flexion and extension of base relative to the ilium, how would you label nutation and counternutation?

Answer 4

NUTATION
-sacral flexion

COUNTERNUTATION

• sacral extension
• base of sacram tilts posterior

Question 5

What motion at the lumbar spine is combined with counternutation of the pelvis?

Answer 5

The base will be extending, meaning the L-S will FLEX to compensate.

E.g. forward bending

Question 6

Nutation of the pevlis results in ___ of the L-S

Answer 6

Extension. E.g. Supine to stand

Question 7

As no muscle act directly on the sacrum, how is movement generated?

Answer 7

Trunk creates sacral nutation moment and shear stress.

GRF though LE and hip create posterior sheer force.

Question 8

Form closure describes passive stability and force closure active; what provide these at the pevlis?

Answer 8

FORM
-SIJ surfaces and ligaments

FORCE
-myofascial structures for SI

Question 9

What exactly does FORM CLOSURE mean in the pelvis?

Answer 9

Form closure describes the stability of the joint from design and anatomy; the sacrum supports the spine and resists forces via high coefficient of friction.

• wedge thicker superiorly
• wider anteriorly
• ridges resist sheer and gliding
• ligmanetous support aids

Question 10

Form closure is useful at rest, but force closure is needed for mobility. What provides this force closure and what does it mean?

Answer 10

Generated by muscles with fiber direction perpedicular to the joint:

POSTERIORLY

1. Lat dorsi
2. Glut max

ANTERIORLY

1. Obliques (pull ilia toward midline)
2. TrA (pull ilia toward midline)
3. Rectus

Compressive forces resist shearing of SIJ in combination with ligaments

Question 11

What do the obliques and TrA use as a fulcum to provide stability of pelvis ?

Answer 11

Interosseous ligament.

Question 12

The multifidus play a cocontration role with the transversus and pelvis floor muscles. What is it?

Answer 12

Stabilize sacrum / SI joint.

Question 13

Which muscles are involved in pelvic girdle control anteriorly, posteriorly and laterally?

Answer 13

ANTERIOR
-abdominal fascia, obliques and contralateral adductors

POSTERIOR

• lat and glut max
• bicep fem at ischium during gait before intial contact

LATERALLY

• glut med/min
• contralateral adductors

Question 14

Name the range of normal lumbopelvic rhythm.

Answer 14

In forward bending, 70* hip flexion, 40* lumbar spine.

Question 15

On initial contact on right, the right ilium rotates ___. In midstances, it moves ___, but not past neutral. In preswing, it rotates ___ past neutral.

Answer 15

Posterior (via hamstring action)
Anterior (hip ext moment)
Anterior (most hip ext)

Question 16

How doe the pelvis behave during stair climbing?

Answer 16

ASCENT
-posterior rotation

DESCENT
-anterior to neutral

Question 17

In gait, pelvic position in ___ during hip flexion and ___ during hip ext.

Answer 17

Anterior, posterior

Question 18

How would you test for pelvic dysfunction and list 3 signs/symptoms.

Answer 18

TEST

• active straight leg raise
• FABER or pelvic compression / distraction

1. SI displacement
2. localize pain at jt or ligaments
3. Pain in sitting or SLS

Question 19

How would you check for abnormal posterior or anterior unilateral rotation, possibly due to a trauma or overuse?

Answer 19

Asymmetry of ASIS or PSIS, reduced posterior torsion.

Question 20

Though uncommon, how can ilial upslips and downslips occur?

Answer 20

UP
-upward jar to leg

DOWN
-childbirth

Question 21

What are ilial inflares and outflares?

Answer 21

IN
-asis on one side closer to midline

OUT
-ASIS further from midline on one side

Likely more related to anterior / posterior torsion

Question 22

What is the likely culprit from an ilial inflare?

Answer 22

Anterior / posterior torsion.

Question 23

An upslip or downslip of the pubic ramus is often associated with ___.

Answer 23

Ilial torsion.

Downslip could be childbirth.

Question 24

What types of activity can cause Osteitis publis?

Answer 24

Kick, running or change in direction activities putting excess strain on symphysis.

Question 25

Diastasis in the pubis can occur post partum and provides significant instability. How many mm is the normal and diastasis gap?

Answer 25

Normal = 4-5mm
Diastesis = 13mm

<25mm treated conservatively