Girls back waist concave indicates that there may be the following situations: 1, this may be a normal physiological depression, in the human body upright due to the lumbar spine itself has a forward physiological curvature, so in the rear observation, you will be able to see the waist has a certain degree of depression. In addition to the location of the bilateral posterior superior iliac spine, due to tendon pulling may cause skin depression, these two parts is often referred to as the lumbar eye. 2, may be due to the lumbosacral angle is too large, this kind of disease is often due to congenital hereditary factors, women are more common. Once attacked, it may cause pain in the lumbosacral region. 3, this situation may be caused by anterior pelvic tilt, such diseases are often due to the hip joints, lumbar and abdominal region of the muscle strength imbalance, resulting in an abnormal position of the pelvis. When this kind of disease attacks, it may also cause the depression of the back waist.4. It may also be caused by the old injury of the waist, for example, there is a old fracture of the waist, and this condition may remain after recovery.