Hip bone consists of three parts: Ilium, ischium and pubis. These three bones meet one another at the acetabulum. The two hip bones articulate with the sacrum at the sacroiliac joint and form the anterolateral walls of the pelvis. They also articulate with each other in front at the symphysis pubis.
The ilium, which is the upper flattened part of the bone, possesses a crest known as the iliac crest. In a living subject, this crest can be felt through the skin along its entire length. The crest ends in the front at the anterior superior iliac spine below which lies the anterior inferior iliac spine. Posteriorly, the crest ends at the posterior superior iliac spine below which lies the posterior inferior iliac spine. Behind the anterior superior iliac spine on the lateral lip of the crest lies a tubercle known as the iliac tubercle. Above and behind the acetabulum, there is a larger notch in the ilium, which is known as the greater sciatic notch.
It is L shaped past of the hip bone and possesses an upper thicker part and a lower thinner part. The upper thicker part is known as body of ischium and the lower thinner part is known as ramus of ischium. A spine, known as the ischial spine, projects from the ischium and intervenes in between the greater and lesser sciatic notches. Ischial tuberosity forms the lower part of the body of ischium. The greater and lesser sciatic notches are converted into greater and lesser sciatic foramina respectively by sacrospinous and sacrotuberous ligaments.
Pubis consists of three parts: the body, superior ramus and inferior ramus. Bodies of the two pubic bones articulate with each other and form the symphysis pubis, which lies in the midline of body. The superior ramus of pubis joins the ilium and ischium at the acetabulum while the inferior ramus joints the ramus of ischium below the obturator foramen. This foramen, in living subjects, is filled by a membrane known as the obturator membrane. Upper part of body of pubis is formed by a crest known as pubic crest. It ends laterally as the pubic tubercle.
On the outer surface of the hip bone is a deep depression, called the acetabulum. It articulates with the head of femur to form hip joint. Inferiorly, the margin of acetabulum is deficient and is marked by the acetabular notch, which is roofed by the transverse acetabular ligament. The articular surface of the acetabulum is limited to horse-shoe shaped surface, which is covered with hyaline cartilage. The floor of the acetabulum is non articular and is known as acetabular fossa.
Hip bone in anatomic position:
In the anatomic position, the front of symphysis pubis and the anterior superior iliac spine lie in the same vertical plane. This means that the pelvic surface of symphysis pubic faces upwards and backwards while the anterior surface of the sacrum faces forwards and downwards.