Corpus ossis ischii

The body enters into and constitutes a little more than two-fifths of the acetabulum.

Its external surface forms part of the lunate surface of the acetabulum and a portion of the acetabular fossa.

Its internal surface is part of the wall of the lesser pelvis; it gives origin to some fibers of the internal obturator.

No muscles insert on the body. Its anterior border projects as the posterior obturator tubercle.

From its posterior border there extends backward a thin and pointed triangular eminence, more or less elongated in different subjects, the ischial spine, origin of the gemellus superior muscle.

Above the spine is a large notch, the greater sciatic notch; Below the spine is a smaller notch, the lesser sciatic notch.