The hip joint, to us ordinary people, is unfamiliar. However, for orthopedics, it is the largest weight-bearing joint in the human body, which is vulnerable to injury, and is a large department in the field of orthopedic science. The common future, that is, the intrinsic, deep joint of the hip bilaterally, contains the head of the femur that we often hear about. Femoral head necrosis is of course only one of the hip disorders. In many elderly people, a gentle fall can easily result in femoral head fractures and intertrochanteric fractures. Gait, the rhythm of walking, is related to a variety of factors, such as eight-legged, K-O leg (rotundity), male and female gender, etc. In women, both hips fluctuate more up and down when walking, while in men, the back and forth rotation is obvious. Some people walk with a left-right sway and obvious shoulder swing; patients with rotund legs are unable to walk in big steps, etc.