Ischium jumping hurdles, basketball, and martial arts. These fractures occur at tubercles (bony projections that lack secondary ossification centers). Avulsion fractures occur where muscles are attached: anterior superior and inferior iliac spines, ischial tuberosities, and ischiopubic rami. A small part of bone with a piece of a tendon or ligament attached is avulsed (torn away). Ischial bursitis (also known as "weaver's bottom") is inflammation of the synovial bursa located between the gluteus maximus muscle and the ischial tuberosity, and is usually caused by prolonged sitting on a hard surface. Adoption of "ischium" into English-language medical literature dates back to c. 1640;
Hip bone the seventh or eighth year, the inferior rami of the pubis and ischium are almost completely united by bone. About the thirteenth or fourteenth year, the three primary centers have extended their growth into the bottom of the acetabulum, and are there separated from each other by a Y-shaped portion of cartilage, which now presents traces of ossification, often by two or more centers. One of these, the os acetabuli, appears about the age of twelve, between the ilium and pubis, and fuses with them about the age of eighteen; it forms the pubic part of the acetabulum. The ilium