Some patients may have a depression on the front of the thigh, and there are several main etiologic factors for this condition: 1. This condition may be a normal muscular sign of the quadriceps muscle on the front of the thigh. The quadriceps muscle has four muscular components, and between the adjacent muscles, there will be some normal muscular gaps in itself, that is, there is a normal depression.2. This condition may be caused by some bony deformities of the femur. For example, if the patient has a deformity of the femur due to hereditary factors, or if the femur has been severely traumatized and the femur is left angulated, there may be an abnormal depression in the thigh.3. This situation may be caused by swelling of the thighs, for example, if the patient has a deep vein thrombosis, there may be a diffuse swelling of the whole lower limb. At this time, if you use your hand or elbow to press down on the front of the thigh, it will cause localized depression. 4, this situation may be caused by long-term pressure, such as when the patient is sitting or standing, the elbow long-term pressure on this area, or due to other reasons, the long-term pressure here, it may also cause depression here.