Osteosarcoma is most commonly found in the epiphysis of the long bones, most commonly the distal femur, proximal tibia and humerus, which are the fastest growing areas in adolescents, and less commonly the flat bones. The earliest clinical symptom of osteosarcoma is pain, occasionally with a history of local trauma, which is initially intermittent and vague, worsening with activity, and gradually becoming constant and severe. These discomforts should be seen promptly to improve the prognosis.