Femoral osteonecrosis is specific to each person from the time it is detected until symptoms appear. How long it takes for femoral head necrosis to occur and develop for a patient to be able to feel it is different for each person. The development period of femoral head necrosis is usually 3-6 months for the average person to be very clear. This period is very important when femoral head necrosis wants to be detected early and stop the early to late transformation. After it is determined and discovered, doctors need to pay attention to it and patients need to pay attention to it, all of which are crucial to stop the development of femoral head necrosis to the late stage.