Posterior Pelvic Tilt is often called the "No Butt Symptom". Having no butt not only takes away from how one's figure looks, but also puts undue stress on the lower back. During normal activities, such as squatting, lifting and bending over, the lower back looses it's curve. This is dangerous for people with normal curve, and it's extremely dangerous for people with flat backs. Having a concave lower curve allows for caution, when it flatten.