The causes of knee pain include trauma, knee osteoarthritis and knee tumor. 1. Trauma: due to the impact of the knee joint, fall and other external factors, resulting in ligament and bone damage in the knee joint, which leads to the symptoms of pain when the patient’s knee joints use force. 2. Knee arthritis: due to degeneration, wear and tear, chronic aseptic inflammation occurs in the patient’s knee joint, when the inflammatory factor is constantly stimulated, it will cause the patient’s knee joint pain when exerting strength. 3. Knee joint tumor: if the patient’s knee joint has occupational lesions, with the continuous growth of the occupational lesions, it will compress the surrounding tissues, which will lead to the symptoms of pain when the patient exerts force on the knee joint. There are many reasons for knee pain, it is recommended that patients go to the hospital in time to improve the relevant examination, to clarify the cause of the disease, and follow the doctor’s instructions for treatment.