Ilium

The ilium is the largest of the three innominate bones of the pelvis. It is a large, flattened, somewhat cup-shaped bone having a large crest anteriorly and posteriorly with four spines serving as sites for muscle and ligamentous attachments. They are also important anatomical landmarks. The iliac crest forms the prominence of the hip and is an important bone for use in surgery requiring bone grafting due to its easy access and its large source of available bone for use. It is also a common site for bone marrow donation in diseases such as leukemia. The crest terminates anteriorly forming the anterior superior iliac spine while just below the termination is the anterior inferior iliac spine. The posterior termination forms the posterior superior iliac spine and below forms the posterior inferior iliac spine.