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AFAB II > Lecture 4: SI Joint > Flashcards

Lecture 4: SI Joint Flashcards

1
Q

SI joint is the junction between what

A

auricular surfaces of the sacrum and illium

tight fitting for stability

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2
Q

what is the key stone of the pelvic ring

A

sacrum

wedged between the two ilia and secured by the SI joints bilaterally

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3
Q

functions of the SI joint

A

transfer weight of the upper body to LE

shock absorber with heel contact

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4
Q

how much back pain is associated with SI joint

A

25% of LBP has SI origin

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5
Q

possibly mechanisms of SI joint pain

A

falling
stepping in hole
childbirth
repetitive unilateral torsion
postural abnormalities

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6
Q

what happens if the LL (lower limb?) is not equal by 1cm

A

5 x increase in compression at SI joint

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7
Q

describe the anterior sacroiliac ligament

A

thickening of the capsule

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8
Q

describe the iliolumbar ligament

A

stabilizer of the lumbosacral joint and SI joint

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9
Q

describe the interosseous ligament

A

fills the gap

strong like syndemosis at the tib/fib

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10
Q

describe the sacrotuberous ligament

A

blends with the biceps femoris

broad attachment

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11
Q

describe the sacrospinous ligament

A

sacrum to ischial spine

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12
Q

name all the ligaments of the pelvic girdle

A

anterior SI
iliolumbar
interosseuos
short and long posterior SI
sacrotuberous
sacrospinous

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13
Q

describe the SI joint innervations and referred pain locations of the SI joint

A

exact spinal level source is uncelar

L5-S3 spinal nerve roots

less often L4-S2

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14
Q

where all can pain be referred from the SI joint

A

ipsilateral lower lumbar region
medial buttock
PSIS
along short and long SI joint ligaments

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15
Q

describe the role of the thoracolumbar fascia in relation to low back/SI

A

important for mechanical stability

most extensive in low back

attaches to the PSIS

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16
Q

describe the sacral joint surface shape and articular cartilage

A

ear shaped or L shaped

vertical short and more horizontal arm

sacral articular cartilage = white/smooth hyaline form 1-3 mm

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17
Q

describe the topography of the sacral joint surface

A

irregular ridges/depressions matched by reciprocal shapes on ilium; interlocking contours prevent downward glide of sacrum

contours = highly variable (age dependent)

articular surface = twisted from superior to inferior like a propeller

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18
Q

describe the cartilage on the ilia side of the SI joint

A

mainly fibrocartilage

1-2 mm thickness

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19
Q

SI joint is a synovial joint; describe the joint capsule

A

2 layers

external fibrous layer that has abundant fibroblasts and collagen fibers

internal synovial layer

20
Q

how does the SI joint change throughout the life span

A

early life = surfaces are generally flat

puberty = surfaces develop ridges/grooves that enhance stability

21
Q

what is innominate motion

A

iliac crest moves on the sacrum

22
Q

what is sacroiliac motion

A

sacrum moves on innominates

23
Q

what are the different methods of investigation of the biomechanics of the SI joint

A

manipulation during surgery/cadaver lab

radiographic (sagittal plane; harder to recognize landmarks)

imaging after insertion of tantalum balls into innominates and sacrum

inclinometers

computerized analysis

24
Q

describe innominate non weight bearing movement at the sacrum during posterior and anterior rotation

A

10-12 degrees posterior rotation cpupled with 6 mm anterior translation

2 degrees innominate anterior RT coupled with 8 mm anterior translation

25
Q

describe innominate weight bearing motion at the sacrum

A

2.5 degree innominate RT and 0.5-1.6 mm translation

26
Q

desribe the motion occuring at the SI joint via the sacrum

A

motion occurs during movement of trunk and extremities

3D RT and translation

3 planes of motion (FLX/EXT, lat FLX, and RT)

1-4 degrees RT and 1-2 mm translation

27
Q

what is the closed packed position of the SI Joint

A

full nutation

standing when loaded

gravity/lig/muscles

28
Q

when is the SI joint unloaded

A

supine

sacrum tends to return to counternutation or less stable position

29
Q

what are the 2 main types of movement WITHIN the innominate bones

A

anterior/fwd motion or nutation (flexion of sacrum)

posterior/bwd motion or counternutation (ext of sacrum)

30
Q

what does nutation mean

A

nodding

31
Q

when does bilateral motion of the sacrum occur

A

with forward/backward bending of the trunk

32
Q

when does unilateral motion of the sacrum occur

A

with flexion and ext of the LEs

33
Q

describe the anatomical definition of nutation

A

relative to innominates

forward motion of the sacral promontory into the pelvis around the coronal axis (medial lateral) anteriorly and inferiorly

glides inferiorly down short arm and posteriorly along long arm

34
Q

the motion of nutation is resisted by what

A

wedge shape of sacrum

ridges/depressions

interosseous and sacrotuberous ligaments

also aided by the muscles that insert into said ligaments

35
Q

describe the anatomical movement of sacral counternutation

A

relative to innominates

sacral base moves posteriorly and superiorly

glides anteriorly along the long arm and superiorly along the short arm

36
Q

counternutation is resisted by what

A

long dorsal ligament

37
Q

why is counternutation less stable

A

sacrotuberous and interosseuos ligaments are lax

38
Q

what sacral movement occurs with forward bend and extension of the spine

A

FB = sacrum counternutates

EXT = sacrum nutates

39
Q

describe sacral torsion

A

coupled motion of rotation and lateral flexion

one side nutates with SB and this induces RT

occurs during walking/gait cycle; not the same as movements with FB and EXT

40
Q

what is the axis of movement of the ilium on the sacrum

A

inferior transverse ligament

41
Q

what is the axis of movement of unilateral RT of the sacrum

A

vertical axis

42
Q

what is the axis for nutation and counternutation of the sacrum

A

middle axis

43
Q

how does the sacrum move with breathing

A

inhale = base of sacrum goes forward and coccyx/ILA go posterior; L/S flexes

exhale is reverse

44
Q

axis of RT for the sacrum during breathing

A

superior axis

45
Q

what are physiological motions

A

anterior motion fization/Nutation

L on L or R on R

46
Q

what are non physiological motions

A

posterior motion fixation/counter nutation

L on R or R on L

47
Q

how does the sacrum move in the normal walking cycle

A

sacrum moves with L torsion on the L oblique axis, return to neutral, and then rotate in R torsion on the R oblique axis, then return to neutral again

posterior nutational movement doesnt appear past neutral in the normal walking cycle

AFAB II (14 decks)

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