Ischium Posteriorly the ramus forms a large swelling, the tuberosity of the ischium, where the hamstrings originate. The inferior ramus of the ischium (ascending ramus) is the thin, flattened part of the ischium, which ascends from the superior ramus, and joins the inferior ramus of the pubis—the junction being indicated in the adult by a raised line. The outer surface is uneven for the origin of the obturator externus and some of the fibers of the adductor magnus; its inner surface forms part of the anterior wall of the pelvis. Its medial border is thick, rough, slightly everted, forms part of
Ischium muscle. Above the spine is a large notch, the greater sciatic notch; Below the spine is a smaller notch, the lesser sciatic notch. The superior ramus of the ischium (descending ramus) projects downward and backward from the body and presents for examination three surfaces: external, internal, and posterior. The external surface is quadrilateral in shape. It is bounded above by a groove that lodges the tendon of the external obturator; below, it is continuous with the inferior ramus; in front it is limited by the posterior margin of the obturator foramen; behind, a prominent margin separates it from the posterior