Necrosis of the femoral head and bone marrow edema syndrome are mainly different in the lesion site, pathological changes, symptoms and other aspects. 1. lesion site: femoral head necrosis is caused by the femoral head of the hip joint. Bone marrow edema syndrome can involve the ankle and knee joints in addition to the hip joint. 2. Pathological changes: Necrosis of the femoral head is a chronic disease due to the obstacle of blood supply to the femoral head, resulting in the collapse of the femoral head and hip dysfunction. Bone marrow edema syndrome is diffuse bone marrow edema in the lesion area, which is self-limiting. 3. Symptoms: Patients with femoral head necrosis mainly have pain in the groin or buttocks or hip, and may have claudication. Bone marrow edema syndrome is pain in the joints, not necessarily hip joints may be knee joints, ankle joints, etc., and activity limitation is the main symptom. When the above symptoms are suspected, it is recommended to seek medical advice, follow the doctor’s instructions for relevant examinations, clarify the cause with the doctor’s help, and carry out targeted treatment or therapy.