Osteosarcoma is mostly seen in adolescent patients aged 10-20 years old, but due to the lack of knowledge of many clinicians, especially those in primary hospitals, some patients are treated as arthritis, or even treated with acupuncture and closure, which delays the best treatment time and causes tumor spread and metastasis in some patients. For example, a 14-year-old female patient had pain in the lower end of left femur 4 months ago, and after one month, she went to local hospital to take X-ray and found bone destruction in the lower end of femur, but because local doctors did not find bone destruction and gave physical therapy, topical creams and painkillers, the pain gradually increased, night pain, swelling and lump in the lower end of femur, and after 2 months, she went to local hospital again and doctors still did not think When he came to our hospital in April, the tumor had already destroyed 12cm of the lower femur and appeared as a large soft tissue mass. In another case, a 20-year-old male patient also presented with pain at the lower end of the femur 4 months ago and went to a local hospital in January, where he was treated with local “ozone” therapy without improvement and gradually worsened, and a mass above the knee joint appeared. Osteosarcoma is most commonly found around the knee joint, therefore, if adolescent patients have pain near the knee joint, the pressure point is not in the patella or joint space but in the lower femur or upper tibia, and the symptoms develop rapidly and the pain is unbearable, especially unilateral limb pain, after excluding common diseases such as meniscal injury, patellar osteochondritis, arthritis, etc., the possibility of malignant bone tumor should be considered, and if necessary, they should go to a higher level hospital in time. To avoid delaying the treatment.