Causes of knee pain: 1. caused by benign diseases, such as trauma, long-term strain, especially in workers and athletes who often use the joints; 2. caused by malignant tumors, such as osteosarcoma, other diseases of the bone and joint, lung cancer, and bone metastases, can cause joint pain. When joint pain occurs in daily life, it is necessary to consider whether it is a benign or malignant disease according to age, gender, occupation, time of symptoms, and the nature of pain.