ischial tuberosity

This is a prominent downward protuberance of the hip bone. As its name suggests, it is part of the ischial component. It is the origin for the hamstring muscles. The ischial tuberosity is also the part of the pelvic girdle that supports the weight of the body when seated. We are able to sit on this bony point without discomfort (and without developing calluses on our bottoms) because our buttocks contain a great deal of cushioning fat.

The ischial tuberosity is covered by gluteus maximus except when the hip is flexed; at this point it can be readily felt.

Because gluteus maximus moves across the outer surface of the tuberosity, a fluid-filled bursa is located between them, to reduce friction. In jobs where there is repetitive backwards and forwards movement of the body when seated, this bursa may become inflamed. In mill towns of Scotland, the condition of "weaver's bottom" was a recognised industrial hazard.