The iliac crest stretches posteriorly from the anterior superior iliac spine [ASIS] to the posterior superior iliac spine [PSIS]. Behind the ASIS, it divides into and outer and inner lip separated by the intermediate zone. The outer lip bulges laterally into the iliac tubercle. Palpable in its entire length, the crest is convex superiorly but is sinuously curved, being concave inward in front, concave outward behind.