In the clinical work of the Department of Osteoarthritis, we often encounter such cases. The patients are mostly middle-aged women complaining of hip pain, and the plain film shows hip dysplasia and osteoarthritic changes, but the patients think they are suffering from femoral head necrosis. Careful inquiry revealed that most of the patients came to the clinic with unsatisfactory results according to the treatment of femoral head necrosis. The primary care physicians mainly based their diagnosis on hip radiographs showing a slightly flattened femoral head, a narrow joint space, the presence of a cystic resorption zone below the weight-bearing area of the femoral head, and the formation of osteosclerosis around it. The patient’s history did not show the common causes of femoral head necrosis, which was clearly a misdiagnosis and misdiagnosis. So how to distinguish between these two diseases? 1, femoral head necrosis female femoral head necrosis often suffer from other diseases, the most common clinical rheumatoid arthritis, systemic lupus erythematosus, thyroid disease, kidney disease and other long-term or short-term use of high doses of hormone therapy caused. In general, the shortest use of hormones is six months, and most patients have long-term use. We call this a high-risk group for femoral head necrosis. Regular MRI of the hip joint is recommended. If the hip joint suddenly becomes painful with limited internal rotation, ischemic necrosis of the femoral head is highly suspected. 2, hip dysplasia complicating osteoarthritis is a gradual development process. In the early stage, the hip joint is only fatigue and discomfort after exertion, which can be relieved after rest. With the growth of age, especially after 45 years old, the affected hip joint begins to experience pain, and the pain gradually increases, and does not ease after rest. The patient has no other diseases, and there is no history of hormone use. 3, imaging differentiation Hip dysplasia and osteoarthritis, the femoral head is mostly subluxed, the femoral head is slightly flattened, but there is no segmental collapse of the femoral head, there is a cystic resorption area above the acetabulum and in the weight-bearing area of the femoral head, the bone sclerosis around the resorption area is obvious, and the joint space is narrow (Figure 1). In the early and middle stages of femoral head necrosis, the joint space was normal, and there were multiple cystic resorption areas in the femoral head, even fused into a single piece, and there was a reactive osteogenic zone formed in the femoral neck. In the later stage, the hemimelia sign or collapse of the weight-bearing area can be seen (Figure 2, 3, 4). CT scan can generally make a clear diagnosis. 4.Only with correct diagnosis can there be correct treatment. Acetabular dysplasia should be treated surgically in childhood, and after middle age, weight control, exercise reduction and oral articular cartilage protector are the main treatments. Femoral head medullary decompression and arthroscopic minimally invasive surgery are ineffective treatments. Femoral head necrosis should be treated according to Ficat staging and hormone dosage should be reduced. If hormones cannot be stopped for other diseases, conservative treatment is poor and joint reconstruction treatment is often required at a later stage.