Most of the buttock depression is a normal physiological phenomenon, but it may also be caused by muscle atrophy and bone diseases. 1. Physiological phenomenon: Individual’s body type factors, fat siltation, lack of exercise, etc., will cause the appearance of buttock depression. 2. Muscle atrophy: For example, trauma, malnutrition, and prolonged bed rest can cause localized muscle atrophy, which can lead to the appearance of a sunken buttock. 3. Skeletal diseases: for example, hip dislocation, lumbar disc herniation compressing the sciatic nerve, hip joint occupational disease, etc., which may also lead to buttock depression. Normal physiological phenomenon does not need to worry and intervention, if there is a disease should go to the hospital for further examination in a timely manner, follow the doctor’s instructions for treatment, so as not to delay the condition.