There are many imaging methods for ischemic necrosis of the femoral head, and the appropriate means should be selected according to the course of the disease. x-ray has the advantages of simplicity and economy, and should be used as a routine means of diagnosis and staging. However, X-ray examination cannot make early diagnosis. The advantages of CT are: ① Suitable for observing the anterior part of the femoral head, which is the common site of necrosis; ② Can detect the early sclerotic changes in the central part, and can clearly show the histological changes of necrotic tissue, recovered tissue and normal tissue; ③ Accurately display the fracture of cortical and subchondral bone caused by ischemic necrosis, and provide the basis for further treatment; ④ Can observe the size of dead bone and the small cystic resorption of cancellous bone ⑤ It can be used for monitoring and definite diagnosis of high-risk patients with clinical symptoms and no abnormalities on X-ray, especially those with a history of hormonal drugs and alcoholism. Magnetic resonance imaging (MRI) is an excellent imaging method for early diagnosis of aseptic necrosis of the femoral head. The advantages of MRI are: (1) no X-ray radiation and no damage to the human body; (2) MRI is very sensitive and can be used for early diagnosis; (3) it can predict the risk of femoral head collapse. ④But MRI has limited popular application value because of its high price. Radionuclide imaging can show the morphology of bones, local blood flow and bone metabolism status of patients in different stages of disease, determine the site of lesions, and provide important information for the diagnosis of aseptic necrosis, judging the condition and observing the efficacy of treatment. In particular, ECT has a high positive rate for diagnosis and can detect lesions not shown abnormally on X-ray, which is helpful for early diagnosis, but its sensitivity is lower than that of MRI. In comparison with each method, when X-ray and CT are positive, the lesion is larger than stage I, so it is difficult to make early diagnosis and perform high-risk monitoring. However, because of its simplicity, low cost and many other advantages, it is still the preferred routine examination method. MRI is a non-invasive examination method for visible bone changes, with the highest degree of safety and the most sensitive and specific among all diagnostic methods, but it is expensive and not suitable for routine examination and regular follow-up. It is not suitable for routine examination and regular follow-up.