1, the main causes: 1.1 a large number of steroid drugs: the use of steroid drugs for the treatment of patients, can inhibit osteoblast osteoclastic synthesis, impede the transformation of former osteoblasts to adult cells, affect the absorption of calcium from the intestine, the occurrence of osteoporosis, trauma can occur after the fine fracture of the bones, reduced resistance, causing bone compression or collapse. Due to compression of marrow cells and capillaries, obstruction of blood flow can lead to osteonecrosis, and if it occurs in the femoral head, it is osteonecrosis of the femoral head. When you find limping when walking, alleviated after rest, and hip discomfort or soreness when sitting down, it suggests that you should be alert to this disease. 1.2 Long-term excessive alcohol consumption: Hyperlipidemia, which occurs after long-term excessive alcohol consumption, is increasing. According to statistics, men who drink more than 250 grams (half a city pound) of alcohol per day will experience elevated free lipic acid in the blood, which is capable of developing vascular embolism in the bone and finally leading to osteonecrosis. In the early stage, hip and knee pain, especially at night or after exertion, and sometimes pain in the inner thighs or knee joints, are mostly diagnosed as rheumatism. Delayed treatment can cause irremediable sequelae.2. Main symptoms: Hip and knee pain, also known as ectopic pain, is the main manifestation of early ischemic symptoms of the femoral head, which is often overlooked because it is “far” from the hip joint and easily misdiagnosed as arthritis or joint injury, but is actually a radiological symptom related to femoral head necrosis. This pain can be obvious due to exertion, trauma, heavy alcohol consumption, excessive activity, stairs and other triggers. 3.What tests can be used to detect early osteonecrosis of the femoral head? X-ray examination is difficult to diagnose early osteonecrosis of the femoral head. Only those experienced specialists can detect the early signs of osteonecrosis from the subtle changes in X-ray plain films. Clinical studies have shown that MRI (magnetic resonance imaging), bone isotope scan and intraosseous pressure measurement all help to detect information of early femoral head necrosis and can find subtle changes in the early stages of femoral head necrosis that cannot be shown by conventional X-ray examination. The early diagnosis of femoral head necrosis is 85.7% with SPECT (isotope bone scan), 80% with MRI, 77% with intraosseous pressure measurement, and 68.4% with conventional bone scan. It is an economic and effective method for early diagnosis of osteonecrosis. 4, draw attention to: 4.1 large amounts of steroids to treat certain diseases patients should be cautious. 4.2 Avoid drinking large amounts of alcohol. 4.3 Early symptoms of osteonecrosis of the femoral head should be found in time to seek medical attention for early detection, early diagnosis and early treatment, so as not to delay treatment and cause irremediable disabilities and sequelae such as femoral head collapse.