Femoral head necrosis, like some other orthopedic diseases, can alert patients to its presence in the form of pain. It is important to be aware of the pain caused by osteonecrosis so that you can detect it when the disease invades. The pain is mainly around the hip joint, inner thigh, groin or radiating to the knee, sometimes only numbness. The pain is mainly vague, dull and intermittent, and it increases with activity, but it is relieved or disappears when resting; due to the influence of each patient’s body and the cause of the disease, the pain varies, and some patients have prolonged and persistent pain no matter resting or walking. As the condition worsens, the pain becomes more intense. At this time, patients with femoral head necrosis may also experience other symptoms to avoid pain, such as limited hip function, limping and squatting difficulties. Why does pain occur in the early stage of femoral head necrosis? Pain represents the severity of the disease to a certain extent. When the femoral head is not accessible to blood, causing bone tissue necrosis, the necrotic bone tissue will produce pain by stimulating the peripheral nerves and constantly communicate the signal of pain to the brain, which is the body’s self-alert system. In addition, necrosis will cause edema of the synovial membrane and edema of the bone marrow, and this inflammatory stimulation will also cause pain. In some patients, when the disease develops to a certain extent, it will cause microfracture or even collapse of the femoral head, which is often a huge pain, and then the pain is often reduced, which is the release of pressure in the femoral head with the collapse, but after the collapse, with the unevenness of the joint surface, secondary cartilage changes, secondary osteoarthritis, the pain preference becomes continuous pain. Femoral head necrosis occurs at the hip joint, and the pain will spread to the inner thigh and knee joint. This is because there are two groups of nerves around the hip joint, the femoral nerve and the closed foraminal nerve, and the two groups of nerves together innervate the knee joint. When a lesion occurs in the knee joint, the pain in the inner thigh and knee is formed through the nerve conduction effect and the reflex action of the spinal cord segment. Even some patients have secondary changes in the lumbar region such as limping, accompanied by low back pain.