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Anatomy · Joints & cartilage

Pubic symphysis

A cartilaginous joint of the pelvis

Pelvis · anterior midline

The pubic symphysis is the midline joint where the bodies of the two pubic bones meet at the front of the pelvis. A pad of fibrocartilage, the interpubic disc, lies between them, and the joint is a secondary cartilaginous joint (a symphysis) that allows only slight movement. It widens a little in late pregnancy and childbirth, and it forms the apex of the pubic arch.

How to spot them

  • ▸Two pubic bodies meet in the midline, with a fibrocartilage disc sandwiched between them
  • ▸Reinforced by the superior pubic ligament above and the arcuate pubic ligament below
  • ▸The inferior pubic rami diverge from it to form the subpubic angle, wider in females
  • ▸A landmark: obstetricians measure from it to the top of the uterus (symphysis-fundal height)

What to know

The joint where the two pubic bones meet in the midline, a fibrocartilage pad between them

Pubic symphysis — a secondary cartilaginous joint.

It widens slightly in late pregnancy and childbirth under the influence of relaxin

Pubic symphysis — separation is called diastasis of the pubic symphysis.

Its upper surface is the starting point for a measurement of the height of the uterus in pregnancy

Pubic symphysis — symphysis-fundal height.

The subpubic angle formed below it is wider in the female pelvis than the male

Pubic symphysis — the pubic arch.

A superior ligament above and an arcuate ligament below reinforce a fibrocartilage pad between two bones in the front midline of the pelvis

Pubic symphysis — the superior pubic and arcuate pubic ligaments.

Key ideas

  • It belongs to the same family as the intervertebral discs: bone, hyaline cartilage on each face, and a fibrocartilage pad between.

Quick-fire facts

  • •OpenStax: the pubis joins the pubis of the opposite side at a specialised joint called the pubic symphysis.
  • •It is a secondary cartilaginous joint (symphysis): amphiarthrosis, slightly movable.
  • •The interpubic disc is fibrocartilage; ligaments reinforce it above (superior pubic) and below (arcuate).
  • •The pubic arch (subpubic angle) is usually wider in females.
  • •Diastasis of the pubic symphysis (separation) can happen in childbirth.
  • •Pelvic girdle pain in pregnancy often involves the symphysis and the sacroiliac joints.
  • •Its Greek root symphysis means 'growing together'.

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