Body of ischium

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

Surfaces
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 Obturator internus.

Borders
Its anterior border projects as the posterior obturator tubercle.

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

Above and below the spine
Above the spine is a large notch, the greater sciatic notch.

Below the spine is a smaller notch, the lesser sciatic notch.