The sacrococcygeal membrane
is a tough fibrous membrane
about 10mm long which extends from the inferior tip of the sacrum
to the body of the coccyx
in humans. It covers the inferior limit of the epidural space
and is analogous to the ligamentum flavum
found at other levels in the spine
It can be found at the apex of an equilateral triangle whose base is formed by the dimples overlying the sacro-iliac joints. The cornua of the sacrum may be palpated with a finger; the sacrococcygeal membrane lies between and inferior to these.