Today, we will introduce two methods of self-testing “long and short legs”: 1. when standing, observe whether the bilateral posterior superior iliac spine line is the same; whether the bilateral popliteal transverse veins are equal; whether the bilateral patella is at the same level; 2. when lying down, observe whether the soles of the lower limbs and the height of the bilateral inner ankles are at the same level. “Long and short legs” can be divided into two categories: structural (real) and functional (pseudo), and there are many reasons for their formation, such as traumatic fracture, stroke, pediatric paralysis, long-term stilts, etc. can cause “long and short legs”. It is easy to cause pelvic tilt, which in turn leads to scoliosis. However, when scoliosis patients are clinically tested for plantar pressure, it is found that many flat feet are prone to biomechanical imbalance of the lower extremities, which leads to long and short legs. If we compare our feet to the foundation of a house, and the foundation is not level, then the house structure must be distorted.