Pubic symphysis
Symphysis pubica
Also known as: symphysis pubis
A secondary cartilaginous joint (symphysis) in the anterior midline uniting the bodies of the two pubic bones through a fibrocartilaginous interpubic disc.
Overview
The opposed symphyseal surfaces are covered by thin hyaline cartilage and united by the interpubic disc of fibrocartilage, which often contains a small slit-like cavity (non-synovial) in adults, especially women. The joint is reinforced by the superior pubic ligament (between the pubic tubercles) and, most strongly, by the inferior (arcuate) pubic ligament, which rounds off the apex of the pubic arch; anteriorly decussating fibres of the rectus abdominis and external oblique aponeuroses add support.
Movement is minimal — a little translation and rotation during walking — but the joint widens in late pregnancy under the influence of relaxin and progesterone. On radiographs the normal gap is ≈4–6 mm in young adults, narrowing with age; physiological widening in pregnancy is a few millimetres, and a gap > 10 mm is generally regarded as pathological diastasis.
- Location
Anterior midline of the pelvis, above the external genitalia.
Anatomy
- Innervation
Branches of the iliohypogastric, ilioinguinal and pudendal nerves.
- Articulations
Symphyseal surface of the right pubis ↔ symphyseal surface of the left pubis (via the interpubic disc).
- Ligaments
Superior pubic ligament, inferior (arcuate) pubic ligament, anterior and posterior pubic ligaments.
Function
- Joins the two hip bones anteriorly, completing the pelvic ring
- Resists tensile, shearing and compressive forces during gait
- Allows slight widening of the birth canal in pregnancy
Clinical significance
Symphyseal diastasis
Separation during difficult delivery or in "open-book" pelvic fractures; severe pain over the symphysis and difficulty walking. Traumatic open-book injuries may tear pelvic veins and the urethra.
Osteitis pubis
Painful non-infectious inflammation of the symphysis in kicking athletes and after pelvic surgery.
Compiled from standard anatomy and physiology references — see the Skeletal System sources. For education only; not medical advice.