MOB TCD
Pubic Symphysis and
Sacroiliac Joint
Professor Emeritus Moira O’Brien
FRCPI, FFSEM, FFSEM (UK), FTCD
Trinity College
Dublin
MOB TCD
Pubic Symphysis
• Secondary cartilagenous
joint
• Articular surface of medial
aspect of body of pubis
• Covered with hyaline
articular cartilage
• Disc of fibrocartilage in
between
MOB TCD
Pubic Symphysis
• 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
MOB TCD
Secondary Changes in Symphysis
• 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
MOB TCD
Sacroiliac Joint
• 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
MOB TCD
Sacroiliac Joint Accessory Ligaments
•
•
•
•
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
MOB TCD
Sacroiliac Joint
• 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
MOB TCD
Sacroiliac Joint
• 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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