Why does femoral head necrosis lead to narrowing of hip joint space?

Like necrosis in other parts of the body, there is a development process, which is divided into three stages: early, middle and late. Patients with early femoral head necrosis did not take protective measures, such as insisting on bearing weight and improper walking, which caused further injury or dislocation of femoral head and narrowed hip joint space. Displacement after femoral neck fracture will also narrow the gap between femoral head and acetabulum; The cartilage of hip joint is damaged by pathological changes and wear, which is also the reason for the narrowing of joint space.