The precursor symptoms of osteosarcoma mainly include unexplained deep or dull pain, localized mass, generalized low-grade fever, pathological fracture and so on. Osteosarcoma, also known as osteogenic sarcoma, is a kind of malignant bone tumor, which is prevalent in adolescents, especially around the knee joint, shoulder joint and so on. Early manifestations and precursors mainly include the following points: 1. Unexplained deep pain or dull pain: unexplained deep pain or dull pain at the extremity tumor end, usually occurring around the knee and shoulder joints, in the early stage, there can be dull pain in the knee or shoulder joints, and the degree of pain gradually aggravates and goes from intermittent pain to continuous pain, characterized by obvious pain at night time, which may affect the rest at night with the aggravation of the disease. 2. Localized lumps: localized swelling can be seen, such as lumps around the knee joints, and the skin surface temperature rises, and the veins become enlarged and congested. 3. Generalized hypothermia: generalized hypothermia, fatigue, and weight loss may occur. 4. Pathological fracture: in case of trauma, children with osteosarcoma may first have pathological fracture as the first symptom. If the above symptoms appear, children and adolescents should go to the hospital in time for consultation, so as to clarify the corresponding diagnosis.