Here are the lumbar vertebrae, the pelvis, and the two femurs. We’ll look at the pelvis by itself.
The pelvis is made up of the two hip bones, or innominate bones, and the sacrum. The fibrous joints which unite them, the two sacro-ilicac joints behind and the pubic symphysis in front, permit almost no movement. We’ll look at the right hip bone by itself.
The hip bone is formed by the fusion of three bones, the ilium, the ischium, and the pubis. The names of these bones give rise to the names of the various features of the hip bone. Let’s look at these features.
This broad bony plate is the wing, or ala of the ilium. Its broad, roughened edge is the iliac crest, an area where many important muscles attach. The iliac crest ends in front at the anterior superior iliac spine, and behind at the posterior superior iliac spine.
This is the ischial spine, with the greater sciatic notch above it, and the lesser sciatic notch below it. This is the ischial tuberosity. The ischial tuberosity is another area where many muscles attach. It’s also the part of the hip bone that we sit on.
The socket for the hip joint is called the acetabulum. This broad smooth area is the articular surface. We’ll see it again in a minute with the articular cartilage intact.
The big hole in the lower part of the hip bone is the obturator foramen. This is the body of the pubis, this is the superior ramus of the pubis, and this is the ischio-pubic ramus. This prominence is the pubic tubercle, to which the inguinal ligament is attached.
It’s helpful to keep in mind that the upper part, and the lower part of the hip bone face in different directions, like my hands. So when we look at the hip bone from in front, like this, we’re looking at the inner aspect of the ilium, and the outer aspect of the pubis and ischium. Now that we’ve looked at the hip bone, let’s bring the sacrum back into the picture. We’re looking at the bones as they’d be in the upright, standing position, and it’s perhaps surprising to see the angle at which the sacrum lies. Its pelvic surface is more nearly horizontal than vertical.
The sacrum is attached to the hip bone not only by the sacro-iliac joint, seen here from behind, but also by two big ligaments, one going to the ischial spine, and one going to the ischial tuberosity, as we’ll see in a minute.