ischium /is″kē·əm/ pl. ischia [L; Gk, ischion, hip joint] , one of the three parts of the hip bone, which joins the ilium and the pubis to form the acetabulum. The ischium comprises the dorsal part of the hip bone and is divided into the body of the ischium, which forms the posteroinferior two fifths of the acetabulum, and the ramus, which joins the inferior ramus of the pubis. The spine of the ischium provides attachment for various muscles, such as the gemellus superior, the coccygeus, and the levator ani. The greater sciatic notch above the spine transmits the superior and inferior gluteal vessels and various nerves, such as gluteal nerves and the sciatic nerve. A notch below the spine of the ischium transmits various ligaments, vessels, and nerves for other parts. The large dorsal tuberosity of the ischium provides attachment for various muscles, such as the adductor longus, the semimembranosus, the biceps femoris, and the semitendinosus. Compare ilium, pubis.
