Pubic symphysis

Last revised by Dr Henry Knipe on 29 Sep 2022

The pubic symphysis (or symphysis pubis) is a midline secondary amphiarthrodial cartilaginous joint of the bony pelvis, uniting both pubic bodies.

The pubic symphysis is a secondary cartilaginous joint, which means there is a wedge-shaped fibrocartilaginous interpubic disc situated between two layers of hyaline cartilage, which line the oval-shaped medial articular surfaces of the pubic bones 1,2

The width of the joint space differs at different ages:

  • ~10 mm at 3 years
  • ~6 mm at 20 years
  • ~3 mm at 50 years

For physiological reasons, women have a greater thickness of the fibrocartilaginous disc, allowing more mobility of the pelvic bones and thereby providing a larger pelvic diameter needed for childbirth.

The pubic symphysis is reinforced by four strong ligaments 2,3:

  • superior pubic ligament: runs from pubic crest to pubic crest
  • inferior pubic (or subpubic or arcuate) ligament: runs from right to left inferior pubic ramus
  • anterior pubic ligament: blends with periosteum laterally as well as the interpubic disc
  • posterior pubic ligament: blends with periosteum of both pubic bodies posteriorly

Other ligaments which attach to the pubic symphysis include:

  • suspensory ligament of the penis
  • pubocervical ligament
  • anteriorly
    • proximal ends of the penile/clitoral shafts
  • inferiorly
    • urethra
    • deep dorsal vein of penis/clitoris
  • posteriorly
    • bladder (separated from the pubic symphysis by the retropubic fat pad)
    • prostate and prostatic venous plexus

Normally very little movement: up to 2 mm shift and 1° rotation 2.

  • congenital widening of the pubic symphysis (rare) 5
  • pubic symphysis cyst (very rare) 8
  • due to anteriorly-situated secondary ossification centers may appear "V-shaped" in adolescents on axial slices but will normally be parallel in adults 1

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Cases and figures

  • Case 1: normal x-ray
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  • Case 2: symphysis pubis cyst
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