Week 9: SIJ

Long posterior sacroiliac ligament

- Runs from PSIS vertically to lower sacrum - Prevents *downward* movement of sacrum

Lumbosacral extension

1. segmental extension of lumbar vertebrae 2. sacrum inititiates with nutation (flexion) while innominates rotate posteriorly to lock 3. once it locks sacrum shifts to counternutation (extension) to move with pelvis as a unit = hip extension

Lumbosacral flexion

1. segmental flexion of lumbar vertebrae 2. sacrum initiates with counternutation (extension) while innominates rotate anteriorly to lock 3. after it locks sacrum shifts to nutation (flexion) to move with pelvis as a unit = hip flexion

There are ______ auricular or ear-shaped articulating surfaces more superior on sacrum of S1-S3.

2 auricular

Each has an auricular articulating surface that corresponds to the sacral articulating surface. This refers to:

2 ilium innominates

How much of the small motion is available?

2-8 degrees

How many fused vertebrae in the sacrum?

5 fused vertebrae S1-S5

What occurs when innominates bones are rotating forward?

ASIS moves inferior & PSIS moves superior

What occurs when innominates bones are rotating backward?

ASIS moves superior & PSIS moves inferior

What are the articulating surfaces of sacrum called?

Ala

interosseous sacroiliac ligament

Ligament between the ilium and sacrum

Force closure refers to

Muscular (muscles generate force) support

ala of sacrum

Wing-like masses of the sacrum

Which is considered close-pack position and sacral flexion? a. nutation b. counternutation

a. nutation

Which one is based on sacral base tips/rotates anteriorly? a. nutation b. counternutation

a. nutation

Two auricular surfaces are ___________ on sacral surfaces. a. thicker b. thinner

a. thicker

This ligament is considered capsular ligaments due to connections to anteroinferior margins of capsule. It covers the anterior aspect of joints. This refers to which type of ligament?

anterior sacroiliac ligament

Which is considered open-pack position and sacral extension? a. nutation b. counternutation

b. counternutation

Which one is based on sacral base tips/rotates posteriorly? a. nutation b. counternutation

b. counternutation

Innominates are covered with _____________ and are ________________. a. dense collagen; thinner b. hyaline cartilage; thinner c. hyaline cartilage; thicker

b. hyaline cartilage; thinner

Where is the symphysis pubis located?

between the two ends of the pubic bones

Form closure refers to

boney congruency

symphysis pubis is what type of joint?

cartilaginous joint

What does the apex of the sacrum articulate with?

coccyx

What is the muscle contribution for extension in lumbopelvic rhythm?

concentric action of glute max and erectors primarily

sacrospinous ligament

connects ischial spines to lateral borders of sacrum and coccyx

sacrotuberous ligament

connects sacrum to ischial tuberosity

What is the primary axis to emphasize for axis of motion of sacrum?

coronal axis and sagittal plane

Sacral "extension" is termed:

counternutation

__________ refer to opposite movement, sacral promontory moves posteriorly & superiorly while sacral apex moves anteriorly.

counternutation

What form pelvic diaphragm? a. support pelvic viscera b. generates, maintains & increases intra-abdominal pressure c. with co-contraction of TA, maintains stiffness of lumbar spine allowing protection and support d. all of above

d. all of above

What is the muscle contribution for flexion in lumbopelvic rhythm?

eccentric action of erectors and glute max primarily

What is the symphysis pubis supported by?

fibrocartilaginous disc, superior pubic ligament, inferior ligament and posterior ligament

What refers to muscular support for the stability of SIJ?

force closure

SIJ acts as a gatekeeper to __________________ from the trunk to LE and vise versa.

force transmission

What would happen if there was no motion available in the SIJ ?

force transmission would not be able to occur.

SIJ works to reduce ____________ during weight bearing activities and act as _____________ as a result.

ground reaction forces; shock absorbers

What are the 2 auricular surfaces covered with?

hyaline cartilage

What does the base of the sacrum articulate with? & what does it support?

inferior facets of L5 ; supports 2 articular facets that face posteriorly

arches from inferior rami on one side of joint to inferior portion of rami on other side to reinforce inferior aspect of joint. What type of ligament is this?

inferior pubic ligament

____________ needs to reciprocally move on SIJ to allow for reciprocal motion such as flexion and extension to be able to move as a unit.

innominates

Which is the MOST important ligaments directly associated to SIJ that create more posterior syndesmoses between tuberosities of sacrum and ilium?

interosseous sacroiliac ligament

From forward flexion to neutral of lumbar pelvic rhythm; what muscle activity is occuring?

large hip extensor muscles such as hamstrings and gluteus maximus

Pelvic floor is made up of

levator ani and coccygeus muscles

A restriction of motion at either the lumbar spine or at hip joints may disturb the rhythm and prevent a person from reaching the toes. This refers to

lumbar pelvic rhythm

Lumbo-pelvic rhythm

movement relationship of the lumbar spine and the hips during forward flexion and extension.

Innominates are considered ___________ and correspond to sacral surfaces.

multiplanar

Sacral "flexion" is termed:

nutation

_______ refer to movement of sacrum wherby sacral promontory moves anteriorly & inferiorly WHILE sacral apex moves posteriorly and superiorly.

nutation

What does 2 ilium innominates refer to?

one side of pelvis that is formed by combining ilium, ischium and pubis together.

From forward flexion to neutral of lumbar pelvic rhythm; coming out from flexion to neutral what is initiating this movement?

pelvis

consist of fibrous membranes that is continous with periosteum of pubic bones. What type of ligament is this?

posterior pubic ligament

What is the SIJ anatomically responsible for?

protecting and supporting visceral structures & serving as attachment sites for ligaments and muscles of both trunk and LE

What is the function of pelvic ring?

provide stability and serve a border for Intra pelvic organs and provide insertion points for muscle

From forward flexion to neutral of lumbar pelvic rhythm; when coming out of flexion position position which direction does the pelvic rotate?

rotates posteriorly on femurs

What is the subclinical amount of motion available?

rotation and translation

What is the articulation between the sacrum and pelvis?

sacroliliac joint

_______________ has a flattened rigid surface that interlocks with one another that promotes stability or FORM CLOSURE due to anatomy design of pelvis.

sacrum

Pelvic ring is made up of the?

sacrum & 2 innominate bones

Which two bones are considered wedge-shaped?

sacrum and coccyx

SIJ is between _____________ and _____________ one on either side.

sacrum and ilium

thick & dense fibrosus band that attaches to pubic crest & tubercles to help support superior aspect of joint. What type of ligament is this?

superior pubic ligament

_______________ _____________ at SIJ can be described by naming the motion according to sacral movement or innominate movement.

symmetrical motion

What type of joint in the posterior portion?

syndesmosis

What type of joint in the anterior portion?

synovial joint

What is the anterior pelvic tilt limited by?

tension in hamstrings or posterior capsule of hip joint

Why is the small amount of motion available required?

to allow force transmission during asymmetrical activities meaning one way versus another.

T or F: at lumbar pelvic rhythm, restriction of motion at one segment may result in hyper-mobility of the unrestricted segment.

true

T or F: there is small amount of motion available but not able to measure or palpate.

true

T or F: two auricular or ear-shaped articulating surfaces are multiplanar and correspond to iliac surfaces.

true

The _________ sacrum represents the five fused sacral vertebrae.

wedge-shaped

SIJ are considered what type of joints?

weight-bearing compound joints

Are hip extensor muscles larger than spinal extensors? explain

yes, they are larger as they can generate more torque which reduces loading on lumbar spine from forceful contractions of the spinal extensors.