Femoral head necrosis is an incurable disease with high incidence, insidious onset and high disability rate at the later stage. Due to the lack of popular knowledge about osteonecrosis and some misinformation, osteonecrosis is the first thing that comes to people’s mind when they have hip pain, and some people are even misdiagnosed as osteonecrosis and over-medicated due to some minor and insignificant hip problems. On the contrary, some of the real patients with osteonecrosis of the femur are very easy to be misdiagnosed as other diseases such as lumbar spinal stenosis because their first symptoms are not hip pain, but knee pain and lower limb soreness, thus missing the best time for treatment. So, when we have hip pain, how to identify whether it is femoral head necrosis? Generally speaking, there are three major typical manifestations of femoral head necrosis. The first is pain, which is manifested as hip pain or pain at the root of the thigh. The second is the limitation of movement, such as the difficulty in doing the “inward eight” movement when standing or squatting when sitting. The third is claudication. What diseases should be distinguished from femoral head necrosis? The following are some of the diseases that we often encounter in our daily lives and need to distinguish from necrosis of the femoral head. 1, acetabular dysplasia: acetabular dysplasia, also known as congenital hip dislocation, is very common in China, mostly seen in young women. The majority of patients often do not have any symptoms in childhood, and only in youth or adulthood do they begin to develop hip pain, which can appear in the root of the thigh, and patients with serious conditions can develop claudication. x-ray can see the acetabular development become shallow, and the femoral head is dislocated upward. 2, hip osteoarthritis: primary hip osteoarthritis occurs mostly in elderly patients, secondary hip osteoarthritis is mostly secondary to late acetabular dysplasia, acetabular fracture, femoral head fracture and other patients. The patient may experience hip pain, which is aggravated by activity, and the hip joint is restricted in flexion and internal and external rotation. x-ray shows narrow joint space, obvious bone growth, and obvious subchondral bone sclerosis in the femoral head and weight-bearing area of the acetabulum. 3.Bursitis of the greater trochanter: The occurrence of bursitis of the greater trochanter of the femur can be caused by trauma, or by repeated wear and tear. The patient presents with limited lateral thigh pain, which can extend to the hip and lateral thigh. The movement of the hip joint is not affected, and there is no abnormal performance on X-ray. 4.Severe osteoporosis: senior women may have severe osteoporosis. Patients will have generalized pain mainly with low back pain, including hip pain, and some patients will also have deformities such as hunchback. The problem can be detected by X-ray examination and bone density examination. 5, lumbar spinal stenosis and lumbar disc herniation: Patients with lumbar spinal stenosis are mostly middle-aged and elderly, and they have typical intermittent claudication, that is, walking a short distance, the patient will have lumbar discomfort or soreness, numbness or pain in both lower limbs, etc., and need to rest for a while, after which they can walk a short distance again. Lumbar disc herniation occurs mostly in young adults, with typical symptoms of hip pain and radiation to the lower extremities, numbness in the lower extremities in some patients, and a herniated disc with posterior dural sac compression visible on MRI of the lumbar spine. All of the above diseases will show similar symptoms to the thigh root pain caused by femoral head necrosis. These diseases will be detected by the doctor after the patient shows symptoms by doing the corresponding imaging examinations, such as X-rays and MRIs. In the case of femoral head necrosis, early imaging examinations are not able to see the problem. Moreover, just as mentioned above, these diseases also have their characteristic manifestations, such as intermittent claudication in patients with lumbar spinal stenosis. By mastering the characteristics of femoral head necrosis and performing the necessary imaging examinations, patients will neither be fooled nor delay the best time for treatment.