What are the early signs of osteosarcoma? Pain and swelling are the earliest signs of osteosarcoma. Among the 796 patients with osteosarcoma reported by foreign scholars, 49% had both pain and swelling as the first symptom, 46% had only pain as the first symptom, and 4% had only painless swelling. In our recent 13-year follow-up study, we found that pain was the first symptom in 58% of 445 patients with osteosarcoma, pain plus swelling in 28%, and painless swelling in only 12%. In addition, it was found that 91% of patients with osteosarcoma younger than 30 years of age had pain as their first symptom, and only 8.1% had painless swelling as their first symptom. In contrast, in patients older than 30 years, although most patients had pain as their first symptom, nearly 20% had painless swelling as their first symptom. This may be related to the different pain thresholds (the maximum amount of pain that can be tolerated) or the treatment of pain in patients of different ages, and also suggests to us that older patients with osteosarcoma are more likely to have only painless swelling in the early stage. It is also important that we should clarify the characteristics of the age distribution of osteosarcoma. It was found that the age group of 10-20 years is the high incidence of osteosarcoma. Therefore, for adolescents aged 10 to 20 years old, they should be highly alert to the occurrence of osteosarcoma when pain occurs around the knee joint, especially when the pain is obvious at night. What is the difference between pain caused by osteosarcoma and growing pains in adolescence? Growing pain is mostly pain after movement of the epiphysis (as in Figure 1) and is associated with the stopping point of the tendon. For example, the patient may feel pain when the doctor presses on the tibial tuberosity stop during check-up, or the patient may feel increased pain when pressing on the goose foot (as in Figure 2). In contrast, the pain of osteosarcoma is mostly persistent and can be felt when the patient is not moving. The pain is especially pronounced after the patient falls asleep. And this nocturnal pain is a very obvious feature of osteosarcoma pain, and is a question that surgeons, especially bone oncologists, must ask their patients. In addition to pain and swelling, if the tumor is relatively fast developing, you can also see angry veins on the surface of the patient’s skin. In addition, some of the affected patients are reluctant to straighten their joints to reduce the pain and will have protective flexion movements, resulting in joint flexion deformity. Girl, 9 years old, with painful swelling as the first symptom and skin surface venous anger