The right and left sacroiliac ( lat. Articulatio sacroiliaca ), sacroiliac joint , sacral iliac joint or shortly sacro-iliac joint is the articulation between the sacrum ( sacrum ) and the iliac ( ilium ).
The sacroiliac joint is a tight, poorly mobile joint ( amphiarthrosis ) with a narrow joint cavity. It is formed from the articular surface on the sacrum and on the ilium . This gives the German-language name sacrum and iliac joint. The two abutting joint surfaces are each called the auricular facies . Fiber cartilage ( ligamenta sacroiliaca interossea ) creates the further connection around these joint surfaces . Due to the joint gap (thought to be frictionless), the joint surfaces of the sacroiliac joint can only transmit normal pressure forces. The tapes ( sacrotuberous ligament , Lig. Sacrospinous , ligaments. Sacroiliaca anteriora , ligaments. Sacroiliaca posteriora and iliolumbalia ligaments. ) Have to compensate for all other forces such an extent that the resulting force always through the instantaneous center of motion of the joint runs (static equilibrium condition real Diarthrosen ) .
Due to a nutation movement in the sacroiliac joint and the associated expansion of the pubic symphysis , the width of the pelvic ring increases, which is of practical importance for the passage of the child's head at birth , which leads to hormonally supported softening of the ligaments. The promontory (Latin for “promontory”) of the sacrum is shifted caudoventrally and the coccyx craniodorsal , whereby the sagittal diameter (conjugata recta) of the pelvic outlet is larger and the conjugata diameter of the pelvic inlet smaller. The sacrum thereby flexes ( flexion ), the iliac bone a rotation (rotation) with displacement of the iliac crest (crista iliaca) backwards ( retroversion , ilium posterior ). The axis of the rotational movement lies in the area of the attachment points of the ligg. sacroiliaca interossea .
Fractures and dislocations of the sacrum and iliac joint can occur in the event of falls, jerky movements and twisting of the pelvis. Acute and chronic inflammation are possible. When ankylosing spondylitis the sacroiliac joints are often affected. The frequently occurring inflammation of the sacrum-iliac joint ( sacroiliitis ) is a diagnostic criterion in early diagnosis.
- Paul Klein, Peter Sommerfeld: Biomechanics of the human joints: Basics, pelvis and lower extremities . Volume 1 of Biomechanics of the Human Joints . Elsevier, Urban & Fischer 2004, ISBN 978-3-437-55203-8 , p. 150 ff.
- bechterew.de - Diagnosis and early diagnosis of ankylosing spondylitis (PDF) ( Memento from October 5, 2018 in the Internet Archive )