5 The SI Joint Flashcards
What are the ligs of the SI jt?
Dorsal:
- posterior sacroiliac: deep to sacrotuberous lig, primary posterior stabilizer of SI jt. Sacrum to ilium.
- sacrospinous: ischial spine to sacrum/coccyx
- sacrotuberous: ischial tuberosity to PSIS, sacrum/coccyx
- interosseous sacroiliac: sacrum to ilium
- iliolumbar: L4-L5 to iliac crest
Ventral:
- anterior sacroiliac: primary anterior stabilizer of SI jt, sacrum to ilium
Is nutation or counternutation considered the close-packed position of the sacrum?
Nutation (base of sacrum rotated anteriorly relative to innominate) (hence why sacrum strongly stabilized posteriorly [weight-bearing])
In what position(s) would counternutation (loose-packed) be found?
typically in non-weight-bearing, particularly lying in supine
How much combined nutation and counternutation is considered normal?
2-4° of rotation
What’s form closure?
theoretical, stable situation where closely articulating jt surfaces do not need external forces to bear a given load
What’s force closure?
jt compression as result of myofascial and ligamentous tension that provides a lateral force in order to facilitate the jt’s ability to bear a vertical load
What are the muscular slings that influence force closure and SI joint stability?
- Posterior longitudinal
- Anterior oblique
- Posterior oblique
- Lateral system
What are the components of the posterior longitudinal sling? What action do they have on SI joint?
- sacral multifidi
- erectors
- thoracolumbar fascia
- long head of biceps femoris via sacrotuberous ligament
All increase force closure – with contraction, nutation/tension on dorsal ligs occurs (hams and erectors tighten sacrotuberous lig while TL fascia and multifidi act directly on sacrum).
What are the components of the anterior oblique sling? What action do they have on SI joint?
- internal obliques
- external obliques
- contralateral adductors
Contraction of abdominals and contralateral adductors stabilize spine and pelvis during single leg stance.
What are the components of the posterior oblique sling? What action do they have on SI joint?
- latissimus dorsi
- contralateral glute max
All contract as synergists to compress SI joint. Glutes tighten sacrotuberous lig. Lats tighten TL fascia.
What are the components of the lateral system sling? What action do they have on SI joint?
- glute med and min
- ipsilateral adductors
- contralateral QL
Ips. adductors and glute med/min work to stabilize pelvis in single leg stance. Contralateral QL works to resist contralateral hip drop.
What are S/S of SI joint dysfunction?
- pain over SI joints, inferomedial to PSIS
- pain on palpation of SI joint
- complaining of low back pain
- radiating pain down legs (L4-L5 dermatomal pattern)
- pain while turning over in bed
- pain with load transfer (sit to stand, standing on one leg)
What are common compensation patterns for SI joint dysfunction?
- piriformis
- iliopsoas
- adductors
- pelvic floor
- fibrosing of joint
How is the stork test performed?
- px transfers load to one leg and brings non-stance hip into flexion at waist height
- we’re looking and feeling for post rotation of non-stance leg innominate/sacral nutation
- in absence of proper pelvic mechanics, we can perform length testing of mm that would prevent post rotation of innominate and sacral nutation
How is the forward bend test performed?
- px standing, therapist has hands on iliac crests and thumbs directly under PSIS’s
- px bend forward segmentally wghile keeping knees extended
- therapist observes and feels for movement of PSIS’s – should move equal amount
- positive is if one PSIS moves further than the other
