Symptoms of recurrent osteosarcoma after surgery are generally consistent with the symptoms before the initial surgery. The main symptoms include: Firstly, localized pain, which is persistent, progressive, and does not alleviate, including pain that worsens at night. Secondly, localized swelling, which usually occurs around the surgical site if limb-sparing surgery was performed, or at the stump if amputation was done. Thirdly, the appearance of systemic cachexia and symptoms of metastasis. Systemic cachexia typically includes weight loss, anemia, fatigue, and loss of appetite. For osteosarcoma, metastasis primarily targets the lungs, where numerous cancerous shadows can be detected. Thus, the main recurrent symptoms of osteosarcoma after surgery include pain, swelling, and cachexia.