Ligament · Pelvis

Sacrotuberous ligament

Ligamentum sacrotuberale

A broad, fan-shaped band at the back of the pelvis, running from the back of the ilium and the side of the lower sacrum and coccyx down to the inner margin of the sitting bone. With the sacrospinous ligament lying in front of it, it converts the two notches in the back of the pelvis into two openings — the greater and lesser sciatic foramina — through which nerves and vessels leave the pelvis for the buttock and the leg. It is not a purely passive band: fibres of gluteus maximus blend into its back surface and the long head of biceps femoris takes part of its origin from it, so it is one of the few ligaments in the body that a muscle can tension directly.