The pelvic outlet is an opening bounded by coccyx, the ischial tuberosities, and the pubis symphysis. The pelvic diaphragm borders the pelvic outlet.

What makes up pelvic outlet?

The pelvic outlet is formed by the ischiopubic rami, ischial spines, inferior symphysis pubis, sacrospinous ligaments, and coccyx. Axial oblique T2WI MR at the same level shows the coccygeus muscle. It arises from the tip of the ischial spine, and the fibers fan out and insert into the lateral side of the coccyx.

What are the inlet and outlet of the pelvis?

The pelvic inlet or superior aperture of the pelvis is a planar surface which defines the boundary between the pelvic cavity and the abdominal cavity (or, according to some authors, between two parts of the pelvic cavity, called lesser pelvis and greater pelvis). It is a major target of measurements of pelvimetry.