The hip bone is composed of three bones - the ilium, ischium, and pubis. These bones come together at the acetabulum, which forms the socket of the hip joint. The ilium forms the upper portion and has several features including the iliac crest. The ischium forms the lower back portion and contains the ischial tuberosity, which the body rests on when sitting. The pubis forms the front of the hip bone and connects the ilium and ischium. It contains features like the pubic tubercle and obturator foramen.