Ischial bone

The ischiadic bone (os ischii) is one of the three components of the pelvic bone (os coxae). It consists of the body of the sciatic bone (corpus ossis ischii) located dorsocaudanically at the acetabulum and the arm (ramus ossis ischii) in the shape of the letter L. Ramus has two parts, one going caudally and the other continuing ventromedial.

Structures of the sciatic bone
On the sciatic bone we distinguish the following structures:


 * tuber ossis ischii, hump of the sciatic – at the transition of the body and shoulder of the sciatic bone. Its roughness causes a spacing of the posterior group of thigh muscles, then the ligamentum sacrotuberale ends here;


 * incisura ischiadica minor, a notch on the descending part of the shoulder of the sciatic bone between the spina ischiadica and tuber ischiadicum. With the help of the ligamentum sacrospinale, ligamentum sacrotuberale and sacrum bone, the exit from the pelvis – foramen ischiadicum minus – is closed, through which the vascular and nerve supply between the small pelvis, perineum and thigh passes;


 * Spina ischiadica, a sciatic thorn, forms the interface between the incisura ischiadica minor and the incisura ischiadica major, protruding in the dorsomedial direction.