The knee pain but the examination can not find the reason to consider sciatica, femoral head necrosis, lumbar intervertebral disc herniation and other reasons, need to be further examined. Knee pain but can’t find the reason for the examination, considering itself is not a knee problem, generally knee osteoarthritis, synovitis, meniscus injury can cause knee pain, if the film examination is fine, consider the pain for the possibility of neuralgia. The common cause of sciatica is pyriformis syndrome, which is caused by pyriformis muscle enlargement compressing the nerves, mainly for the back side of the knee pain, walking pain, check the pyriformis MRI film can be clearly diagnosed. Necrosis of the femoral head can radiate to the pain of the knee joint, and the pain point cannot be felt in the knee joint, and the activity of the hip joint is limited, and walking is lame. The diagnosis can be clarified by MRI of the hip joint. Herniated lumbar disc can radiate to knee pain, and some of them can radiate to calf pain and numbness, which can be clearly diagnosed by lumbar MRI film. If you can’t find out the cause of your knee pain, you should go to the hospital for further diagnosis through physical examination and auxiliary examination, and then treat the cause of the disease.