SIJ Flashcards
Describe the SIJ.
A part synovial and part syndesmosis joint with the sacral cartilage resembling hyaline cartilage and the iliac cartilage resembling fibrocartilage. The joint functions to transmit axial loads from the upper body to the legs and vice versa.
How does the orientation of the SIJ make it difficult to establish a specific axis of motion?
The axes of motion lie in a transverse plane at the level of S2 but varies considerably due to contour variations
Describe the concept of force closure and form closure.
Stability is provided to a joint by form closure due to the interlocking surfaces (SIJ) or by force closure due to ligament and muscular action.
Name and describe the sacral ligaments.
Anterior SI ligament: covers ventral aspec of the joint and extends from the sacral ala and anterior sacral surface to the anterior surface of the ilium
Sacrospinous ligament: originates from the inferior lateral angle of the sacrum to the ischial spine of the ilium
Sacrotuberous ligament: originates from the sacrum to the ischial tuberosity
Describe the sciatic notches.
greater sciatic notch is superior of sacrospinous ligament, while the lesser is inferior of the ligament
Which muscles contribute to the stability of the SIJ?
Adjacent muscles, including the quadratus lumborum, multifidus, erector spinae, gluteus minimus, piriformis, iliacis, and lats, contribute to the strength of the joint capsule and ligaments.
What are the nerves of the lumbosacral plexus?
Tibial nerve (L4-S3): innervates the medial HS, adductor magnus, posterior compartment of leg, and foot intrinsics.
Fibular nerve (L4-S2): lateral HS, lateral compartment of leg, EDB of foot
Pudendal nerve (S2-S4)
Superior gluteal nerve (L4-S1): glute medius, minimus, TFL
Nerve to quadratus femoris and inferior gemellus (L4-S1)
Inferior gluteal nerve (L5-S2) glute max
Nerve to obturator internus and superior gemellus (L5-S2)
Nerve to piriformis (S1-S2)
What are the functional differences between the male and female pelvis?
Male: weight is directly vertical to axis of support of the legs, narrower and stronger
Female: weight is posterior to axis of support, wider, and weaker
Describe the influence of hormones on the SIJ.
Relaxin is present throughout pregnancy and between ovulation and menses that make the SIJ more lax
Does motion occur at the SIJ?
Yes, but very minimal
Describe movement of the SIJ during ambulation.
The iliac moves backward during the swing phase of gait.
Describe the pain referral pattern of the SIJ.
As mapped by injection, pain is unilateral to the involved side in an area approximately 3 by 10 cm immediately inferior to the PSIS.
What common medical conditions affect the SIJ?
Ankylosing spondylitis (AS) begins as inflammation involving the synovium of the SIJ. Ligaments are transformed to bone. It is most common in Indians and whites, and more common in males under 40. Symptoms usually begin in the lumbar spine and can affect the SIJ.
