Sciatica to knee pain, may be due to hip synovitis, femoral head necrosis, lumbar spine lesions and other causes. 1. Hip synovitis: the hip joint is located above the hip bone, the top part of the thigh, and the synovial membrane is an important part of the hip joint, when the hip synovitis occurs, due to the stimulation of inflammation, it may cause pain from sciatica to the knee, and may be accompanied by localized redness and swelling of the hip joint, and limitation of the hip joint activities and other symptoms. 2. Necrosis of the femoral head: this disease is usually caused by the interruption of blood supply to the femoral head or damage to the femoral head, which can lead to structural changes in the patient’s femoral head, resulting in the collapse of the femoral head, which may cause pain from sciatica to the knee, and may be accompanied by symptoms such as claudication or difficulty in walking. 3. Lumbar spine lesions: commonly seen in lumbar disc herniation, lumbar spinal stenosis and other diseases, which can easily lead to sciatic nerve root compression, which may cause sciatic to knee pain, and may be accompanied by lower limb numbness, weakness and other symptoms. Sciatica to knee pain, may also be caused by other reasons, if the symptoms can not be relieved, should be as early as possible to seek medical treatment, through the perfect relevant examination, diagnosis of the cause, give targeted treatment.