The ilium is a paired bone that forms the uppermost and largest part of the hip bone.

Parts

• Body of the ilium - the central portion of the ilium forming the upper third of the acetabulum;
• Wing of the ilium - the large expanded portion of the ilium.

Landmarks

• Arcuate line - a prominent bony ridge on the internal surface of the ilium separating the body from the wing, also forming the boundary between the false pelvis and true pelvis
• Iliac crest - the superior border of the iliac wing that extends between two bony projections:
  • Anterior superior iliac spine
  • Posterior superior iliac spine
• Anterior inferior iliac spine and posterior inferior iliac spine
• Iliac fossa - a concavity forming the internal surface of the wing of the ilium
• Sacropelvic surface, which features the:
  • Auricular surface - an ear-shaped surface within the sacropelvic surface of the ilium, which articulates with the sacrum
  • Iliac tuberosity - a roughened area behind and above the auricular surface
• Gluteal surface, which presents three ridges: the anterior, posterior, and inferior gluteal lines