Knee pain can be caused by the following reasons: First, severe osteoarthritis of the knee joint, which can involve the cartilage, meniscus and soft tissues of the knee joint and lead to damage, resulting in special pain in the knee joint, especially when cold, strain, pain is very obvious, then the knee joint X-ray, CT to diagnose and treatment. Second, gout, gout can involve the knee joint and lead to severe pain in the knee joint, which can have a significant restriction of movement of the knee joint, swelling of the joint, often accompanied by significant fluid accumulation, then blood tests and x-ray of the knee joint should be taken for diagnosis and early treatment. Third, tumors of the knee joint, when there is a malignant tumor of the knee joint, such as osteosarcoma or Ewing’s sarcoma, synovial sarcoma and other tumors, there can also be significant pain in the knee joint, then it is necessary to check the MRI of the knee joint to diagnose and treat early.