From the posterior border of the body of the Ischium there extends backward a thin and pointed triangular eminence, the ischial spine, more or less elongated in different subjects. It can serve as a landmark in pudendal anesthesia[Wikipedia:Ischial_spine].

BTO places this in the vertebral column

spine of ischium, the ischial spines, spine of the ischium

uberon

UBERON:0009000

Ischial spine

• coccygeus muscle
• superior gemellus muscle
• iliococcygeus muscle