Sitzbeinstachel - Spina ischiadica
From the posterior border of the body of ischium there extends backward a thin and pointed triangular eminence, the ischial spine, more or less elongated in different subjects, situated between the greater and lesser sciatic notches. The external surface of the spine gives attachment to the Gemellus superior, its internal surface to the Coccygeus, Levator ani, and the pelvic fascia; while to the pointed extremity the sacrospinous ligament is attached.
This definition incorporates text from a public domain edition of Gray's Anatomy (20th U.S. edition of Gray's Anatomy of the Human Body, published in 1918 – from http://www.bartleby.com/107/).
Allgemeine Anatomie > Bones; Skeletal system > Skeleton appendiculare > Ossa membri inferioris > Beckengürtel > Hüftbein > Sitzbein > Sitzbeinstachel