The ilium (see Figure 3.28) is the largest of the three bones and provides an extensive surface for attachment of muscles and tendons. It is in the form of a ridge superiorly, the iliac crest. Anteriorly, the iliac crest forms a prominence called the anterior supe-rior iliac spine. Posteriorly, the crest ends at the pos-terior superior iliac spine. Posteriorly and inferi-orly, there is a deep notch called thegreater sciaticnotch. Other important landmarks on the ilium areshown in Figure 3.27.