The inferior ramus of the pubis fuses with the inferior ramus of the ischium. The superior ramus helps form the acetabulum and is ridged by an upper pectineal line and lower obturator crest. The pubis is the inferior, anterior portion of the hip bone consisting of a superior ramus, body, and inferior ramus. The ischial tuberosity lies at the posterior and inferior surface of the ischium and is divided into a medial part which serves as an attachment for the biceps, semitendinosus, and semimembranosus muscles, and a lateral part to which the sacrotuberous ligament is attached. The concavity between this spine and the inferior ramus is called the lesser sciatic notch. At the posteromedial junction, the bone has a projection called the ischial spine-the concavity between this spine and the posterior inferior iliac spine forms the greater sciatic notch. The ischium is the inferior posterior portion of the hip bone it consists of a superior body and an inferior ramus. The arcuate line runs obliquely forwards from this, defining part of the pelvic brim. The posterior part of the medial surface contains the auricular surface for articulation with the sacrum. Medially, the iliac fossa is concave and very thin at its deepest part, containing a large bursa for the overlying iliacus muscle. Inferior to these lie their inferior equivalents. Anteriorly this crest ends at the anterior superior iliac spine and posteriorly at the posterior superior iliac spine. The rim of the superior ala is called the iliac crest. The ilium is the physically largest of the three pelvic bones. This structure is located superiorly relative to the pubis and ischium and is composed of a wing-shaped portion called the superior ala along with the inferior body. Below this brim is defined as the ‘true pelvis,’ whereas the ‘false pelvis’ above this line is, in fact, part of the abdominal cavity. The pelvic brim is the line formed by the continuation of the pectineal line on the pubic bones, the arcuate line of the ilium, and the ala of the sacrum.

Together, these bones form the hip or innominate bone they articulate in the midline with the sacrum posteriorly and anteriorly at the interface between the two pubic bones. Each hip bone consists of three bones: the ischium, ilium, and pubis.

Is the pelvis a flat bone