The arcuate pubic ligament (inferior pubic ligament) is a thick, curved fibrous band forming the inferior boundary of the pubic symphysis. It arches across the inferior surface of the symphysis between the two inferior pubic rami, filling the pubic arch and forming the apex of the subpubic angle. It is the strongest of the pubic symphysis ligaments and corresponds to the posterior longitudinal ligament at other spinal levels.
Resists distraction and inferior separation of the pubic bones, maintains the integrity of the subpubic arch during walking and running, and limits anteroposterior translation at the pubic symphysis.
The arcuate pubic ligament is the primary structure resisting symphyseal diastasis. In open-book pelvic ring injuries, the symphysis widens as the arcuate and anterior pubic ligaments fail, with the posterior sacroiliac ligaments determining whether the injury is stable or unstable. In obstetric symphysiolysis, the arcuate ligament attenuates due to relaxin-mediated softening during pregnancy, allowing painful symphyseal motion. The ligament is also relevant in perineal surgical approaches and during mid-urethral sling procedures.
Disruption of the arcuate and anterior pubic ligaments from high-energy pelvic trauma produces symphyseal widening greater than 2.5 cm, an open-book injury requiring external fixation or plate fixation to close the ring and restore pelvic stability.
Relaxin-mediated attenuation of the arcuate and anterior symphyseal ligaments during pregnancy produces painful symphyseal motion, managed conservatively with a pelvic brace, physiotherapy, and analgesics, resolving after delivery.
