SIJ iRA/tRA Flashcards
Anterior vs posterior surface of sacrum
anterior - concave, smooth
posterior - convex, rough
Where is the sacrum width greater?
Width greater posteriorly at S1, greater anteriorly at S3
If lumbosacral angels are decreased that means what?
more direct transfer
If lumbosacral angels are increased that means what?
shear on L5/S1
function of interosseus sacroiliac ligament
secure bony interlocking, strong bind of sacrum and ilium
What prevents anterior separation of the SI joint?
anterior sacroiliac ligament
What does the long posterior sacroiliac ligament do?
prevent counter-nutation of sacrum with respect to ilium
What does the short posterior sacroiliac ligament do?
prevent posterior flaring/separation of joint
function of the sacrospinous ligament
prevent nutation
function of the sacrotuberous ligament
prevent nutation
muscles that anterior rotate the pelvis
psias/iliacus and rectus femoris
muscles that posterior rotate the pelvis
hamstrings
action of the piriformis
ER when hips extended
Abduction when hips flexed
What does the SIJ tilt forward and downward, rotate around?
Bonnaire’s tubercle
What is the function of the SIJ?
- bony locking mechanism
- prevent downward gliding of the sacrum under body weight
- relieves twisting moment on pelvic ring
When does elevation and depression of the SIJ develop? What is this good for?
2nd decade
- good for structural stability
When does articular cartilage start to decrease depth of surface in SIJ?
8th decade
What is nutation? What does this cause the wings to do?
base moves anteriorly and inferiorly and coccyx moves posteriorly
- wings approximate and ischial tuberosity increase in proximity
What is counternutation?
base moves superior and posterior and coccyx moves inferior and anterior
What is the axis of the SIJ during contralateral prone hip flexion?
pubic symphysis to greater sciatic notch
What is the axis of the SIH during contralateral prone hip extension?
pubic symphysis to between ischium and coocyx
With extension of the lower limb, the ipsilateral pelvis twists _______
forward
- tension on iliofemoral ligament draws anterior ilium downwards, rotating pelvis
With flexion of the LE, ipsilateral pelvis twisted __________
backwards
- tension on hamstrings draws ischium forwards, causing the pelvis to rotate
