Where do osteosarcomas tend to develop? Is it always around the knee? Statistics from American and European scholars show that 70% of osteosarcomas grow around the knee. In a 13-year follow-up, Beijing 301 Hospital found that 74% of osteosarcomas of the limb occurred around the knee. The most common sites of osteosarcoma are: distal femur, proximal tibia and proximal humerus, in that order. What are the causes of osteosarcoma? Can trauma cause osteosarcoma? What are the causes of osteosarcoma? Is it possible to prevent osteosarcoma from occurring? In fact, some cancers have found relatively clear causative factors, for example, nasopharyngeal cancer is very related to the environment and is highly prevalent in Guangdong; esophageal cancer is related to diet, for example, eating more rough food can induce esophageal cancer; lung cancer is related to smoking and the environment. Unfortunately, however, primary osteosarcoma, unlike the above diseases, currently has no clear cause. However, secondary osteosarcoma, at present, has a relatively clear cause – Paget’s disease, i.e. Paget’s disease is prone to malignant transformation into osteosarcoma. However, Paget’s disease is relatively rare in China. There are two peaks in the distribution of osteosarcoma incidence in foreign countries: adolescents aged 10~20 years old and elderly people aged 50~60 years old. Among them, the second peak (50~60 years old) of osteosarcoma patients is usually caused by the malignant transformation of Paget’s disease. Age of onset of osteosarcoma