The hips and butt feature three pairs of bony landmarks – two on the Ilium and one on the Femur. The Anterior Superior Iliac Spine (A.S.I.S.) is the anterior extremity of the Iliac Crest, and the Posterior Superior Iliac Spine (P.S.I.S) is its posterior extremity. The Greater Trochanter is a prominent bony landmark of the Femur and the widest part of the hips.