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Pubic Symphysis and Sacroiliac Joint Professor Emeritus Moira O’Brien MOB TCD Pubic Symphysis and Sacroiliac Joint Professor Emeritus Moira O’Brien FRCPI, FFSEM, FFSEM (UK), FTCD Trinity College Dublin

Pubic Symphysis Secondary cartilagenous joint MOB TCD Secondary cartilagenous joint Articular surface of medial aspect of body of pubis Covered with hyaline articular cartilage Disc of fibrocartilage in between

Pubic Symphysis MOB TCD A cavity may develop in the disc, but it is not lined with synovial membrane The arcuate or inferior ligament is stronger than the superior pubic ligament

Secondary Changes in Symphysis MOB TCD There is normally very little movement at the pubic symphysis, except during the latter months of pregnancy Infection, e.g. Reiter’s syndrome Loss of hip mobility, especially internal rotation Fricker, 1997

Sacroiliac Joint Modified synovial plane joint MOB TCD Modified synovial plane joint The auricular articular surfaces of the sacrum and the Ilium The hyaline cartilage on the articular surfaces is rough The capsule is attached just beyond the articular margin The interosseous sacroiliac ligament is one of the strongest ligaments in the body and is posterior to the joint This articulation is almost immobile

Sacroiliac Joint Accessory Ligaments MOB TCD Sacrotuberous ligaments Sacrospinous ligaments Iliolumbar ligaments Posterior superior iliac spine is middle of the joint posteriorly, it is superficial During gait, the amount of accessory movement at the sacroiliac joint helps to protect the lumbar intervertebral discs

Sacroiliac Joint MOB TCD Decreasing the torsional stresses associated with pelvic rotation Movement at the sacroiliac joint also helps to decrease forward shearing at the L5/S1 junction during the hip extension phase of gait More movement during pregnancy Tigney & Lindsay et al., quoted in DeMann, 1997

Sacroiliac Joint MOB TCD Secondary changes may arise in the joint due to anatomical malalignments and biomechanical factors Leg length discrepancies Poor running technique The arms swing across the front of the body, causing stress at the joint

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