Bony landmark · Pelvis

Ischial tuberosity

Tuber ischiadicum

The ischial tuberosity is the sit bone: the thick rounded knob at the bottom of the pelvis that carries your weight whenever you sit upright. It is the origin of all three hamstrings — the long head of the biceps femoris, the semitendinosus and the semimembranosus — along with the ischiocondylar part of the adductor magnus, and the sacrotuberous ligament ties it back to the sacrum. Because the hamstrings run from this point all the way past the knee, every time the hip hinges forwards they pull directly on it.