Body of ischium

The ischium consists of two main parts: a body of ischium and a ramus.

The body of ischium is a dense mass of bone that is situated below and behind the acetabulum. Its upper end articulates with the ilium and the superior ramus of the pubis. The lower end thickens to form the ischial tuberosity.

The body of ischium has three borders: anterior, posterior, and lateral:

• The anterior border forms the posterior boundary of the obturator foramen.

• The posterior border extends upwards and joins the posterior border of the ilium, forming part of the greater sciatic notch. Below, the posterior border features the ischial spine and the concavity known as the lesser sciatic notch. Further down, the lower border culminates at the ischial tuberosity.

• The lateral border descends along the lateral aspect of the ischial tuberosity.

The body of ischium also possesses three surfaces: femoral, pelvic, and dorsal:

• The femoral surface faces outward and lies between the anterior and lateral borders.

• The pelvic surface faces inward and lies between anterior and posterior borders. It is smooth and contributes to the lateral wall of the true pelvis. Above, it continues as the sacropelvic surface of the ilium.

• The dorsal surface resides between the lateral and posterior borders. It continues above as the gluteal surface of the ilium.

The ischial tuberosity contains a transverse ridge, dividing it into upper and lower halves. The upper half is further divided by an oblique ridge into superolateral and inferomedial parts, while the lower half is subdivided by a longitudinal ridge into outer and inner regions.

For details regarding muscles and ligaments attached to ischium please refer to the link here: ischium.