Its unclear what you mean by "crest". The human femur has over 25 named aspects referring to different areas, ridges, sides,etc. of the bone. Some of these are where the bone connects to another bone, others are places where muscles attach. The names are importent so doctors and scientists can talk about all these parts of the bone and know what one another is referring to. For example, if a doctor says, "there is a fracture of the medial epicondyle of the patient's femur," other doctors can know what he's talking about. One named aspect of the femur is the intertrocanteric crest which bridges the greater and lesser trochanters on the proximal posterior side of the femur and acts as the attachment site for the quadratus femoris muscle.