Inferior pubic ligament

At a glance

English

Inferior pubic ligament

Latin (TA2)

Ligamentum pubicum inferius

System

Ligament

Region

Abdomen

Side

Single, on the midline

About the inferior pubic ligament

The pubic symphysis, the midline joint at the front of the pelvis, is held by a fibrocartilage disc and four ligaments named by their position. The ones above and below are strong; those in front and behind are weaker. The inferior pubic ligament, also called the arcuate or subpubic ligament, is the strongest of the set and lies under the joint.

In shape it is a thick triangle of fibres arched across the midline. Its sides attach to the inner borders of the inferior pubic rami of both bones, and its upper border blends with the underside of the interpubic disc. Its lower edge is free and curved, and forms the smooth, rounded apex of the pubic arch, the angle between the two inferior rami. Because of this curve, the angle at the top of the arch is blunted rather than sharp.

Below the free edge, a narrow gap separates the ligament from the front edge of the perineal membrane. Small vessels pass through this gap between the pelvis and the perineum.

Working with the disc and with its partner above, the inferior ligament keeps the two pubic bones together and resists their separating, shearing up and down, or twisting against each other, movements that are normally only a few millimetres. Forces from walking, running and standing on one leg pass through the joint, and the inferior ligament takes much of the strain when the bones are pulled apart. Injury to it can occur in high-energy pelvic fractures that open the front of the ring, and chronic stress at the symphysis in athletes, called osteitis pubis, causes pain over the joint.

Attachments and function

Attaches from

The inner border of the inferior pubic ramus of one side.

Attaches to

The inner border of the inferior pubic ramus of the other side, blending above with the interpubic disc.

Function

Binds the two pubic bones together from below and resists separation, shear and twisting at the pubic symphysis.

Nerve supply

The symphysis receives twigs from the pudendal nerve and from the ilio-inguinal and genitofemoral nerves.

Blood supply

Pubic branches of the obturator and inferior epigastric arteries, with twigs of the internal pudendal artery.