Exam 1 - SI joint and axial skeleton muscle and joint interactions Flashcards
describe the sacroiliac joint
junction between auricular surfaces of the sacrum and the ilium
tight fitting for stability
shock absorber with heel contact
what is keystone of the pelvic ring
sacrum
what motions increases risk of LBP due to the SI joint
falling
stepping in a hole
childbirth
repetitive unilateral torsions
postural abnormalities
describe the anterior sacroiliac ligament
thickening of the capsule
describe the iliolumbar ligament
stabilizer of lumbosacral joint and SIJ
describe the interosseous ligament
fills the gap
strong like a syndesmosis at tib/fib
describe the sacrotuberous ligament
blends with biceps femoris
runs from sacrum to ischial tuberosity
describe the sacrospinous ligament
runs from the sacrum to ischial spine
where can SIJ pain be located in the body
ipsilateral lower lumbar region
medial buttock
PSIS
along short and long SIJ ligaments
describe the thoracolumbar fascia
important role in mechanical stability of low back and SIJ
attaches to PSIS
where is the throacolumbar fascia the most extensive
in the lower back
anterior, middle, posterior layers of the thoracolumbar fascia surround various muscle groups
describe the cartilage and the joint surface of the SIJ on the sacrum side
ear-shaped or L-shaped
vertical short and more horizontal long arm
sacral articular cartilage is normally white and smooth (hyaline)
irregular ridges and depressions are matched with shapes of the illium that allow the sacrum and ilium to interlock
how is the articular surface of the sacrum twisted
above downwards
like a propeller
describe the cartilage on the SIJ on the ilia side
cartilage is mainly fibrocartilage 1-2 mm thickness
describe the sacroiliac joint and the joint capsule
synovial joint
joint capsule is 2 layers
- external fibroblasts and collagen fibers
- inner synovial layers
how does the sacroiliac joint change with aging
surface changes from flat in young age to ridges/grooves throughout puberty
what is the purpose of the ridges/grooves of the SIJ
develops through puberty
enhances stability
describe the osteo- and arthrokinematics of the iliac crests on the sacrum
iliac crest move on the sacrum
innominate motion
t/f
movement at the SI joint does not affect movement at the pubic symphysis
false
movement at the SI joint does affect movement at the pubic symphysis
describe the osteo- and arthrokinematics of the sacrum on the iliac crest
sacrum moves on innominates
sacroiliac motion
describe the osteo- and arthrokinematics of the sacrum on the iliac crest
sacrum moves on innominate
sacroiliac motion
what are the investigation methods of the SIJ biomechanics
manipulation during surgery/cadaver
radiographic
imaging after insertion of tantalum balls into innominate and sacrum
inclinometers
computerized analysis
what are the NWB motions occurring within the pelvis at the SIJ innominates
10-12 degrees innominate posterior rotation coupled with 6 mm anterior translation
2 degree innominate anterior rotation coupled with 8mm anterior translation
what are the WB motion occurring within the pelvis at the SIJ innominates
2.5 degree innominate rotation and 0.5-1.6 mm translation
t/f
motion at the SIJ occurs during movements of the trunk and extremities
true
what side of the sacrum dictates the motion
anterior side
t/f
movement of the SIJ does not continue throughout life
false
movement of the SIJ continues throughout life
what are the 3 planes of motion of the sacrum in the SIJ
flexion/extension
lateral flexion
rotation
how many degrees of rotation and translation occurs a the sacrum in the SIJ
1-4 degrees of rotaion
1-2 mm tralslation
what position is closed packed position of the sacrum in the SIJ
nutation - standing when loaded
what position is open packed position of the sacrum in the SIJ
when supine - unloaded
sacrum tents to return to counternutation or less stable
what is the anterior/forward motion or nutation
flexion of the sacrum
what is posterior/backward motion or counternutation
extension of the sacrum
what does nutation mean
nodding
bilateral motion of sacrum occurs with what motion of the trunk
forward/backward bending of the trunk
unilateral motion of the sacrum occurs with what motion
flexion/extension of the lower extremities
describe sacral nutation relative to the innominate
forward motion of the sacral promontory into the pelvis
coronal axis
anteriorly and inferiorly
the sacrum glides __ does the short arm and ___ along the long arm
the sacrum glides inferiorly on the short arm and posteriorly along the long arm
what resists motion of the sacrum during nutation
wedge shape of sacrum
ridges/depressions in point surface
interosseous and sacrotuberous ligaments
describe sacral counternutation relative to the innominates
sacral base moves posteriorly and superiorly
glides anteriorly along long arm and superiorly up short arm
t/f
coutnernutation of the sacrum is considered to be more stable than nutation
false
counternutation of the sacrum is considered to be less stable than mutation because sacrotuberous and interosseous ligaments are lax
what limits motion during counternutation of the sacrum
long dorsal ligament
during a forward bend, the sacrum (nutates/counternutates)
counternutates
during extension, the sacrum (nutates/counternutates)
nutates
during anterior rotation on of the pelvis/innominate, what is the glide at the SIJ
inferoposterior glide
during posterior rotation of the pelvise/innominate, what is the glide at the SIJ
anterosuperior glide
during walking/gait cycle motion sacral (is/is not) the same as forward/backward bending
is not
what happens during unilateral motion of the sacrum
one side nutates with side bend
induces mutation
what occurs during sacral torsion
coupled motion of rotation and lateral flexion
what is the middle axis of the sacrum
nutation (flexion) and counternutation (extension)
postural
S2
What is the vertical axis
Unilateral rotation
What are the physiological motions
Anterior motion fixation/nutation
L on L
R on R
What are non-physiological motions
Posterior motion fixation/counternutation
L on R
R on L
Describe the R on R or physiological motions
L sacral anterior nutation/rotation R
Occurs around R oblique axis
Describe how the sacrum moves during the normal walking cycle
Sacrum moves with left torsion on the left oblique axis
Return to neutral
Rotate right torsion n the right oblique axis
Return to neutral
T/f
Posterior nutation movement does not appear past neutral in the normal walking cycle
True
Physiologic or non?
- Same side axi as + forward sit
- sphinx sacral sulcus gets more even when in extension
- negative spring on L5
Physiologic
Physiological or non?
- other side axis as + forwar sit
- sphinx sacral sulcus will get less even when in extension
- + spring on L5
Non-physiologic
