12-year-old boy below the knee suddenly pain for ten days possible causes are trauma, septic osteomyelitis, bone tumors, etc., different diseases treatment varies, including anti-infective treatment, surgical treatment, radiotherapy and so on. 1. Trauma: 12-year-old boys are more active and easily injured. If the patient has a history of fall or injury, no fracture can be treated conservatively by X-ray radiographs, including rest and braking of the affected limb, etc. If a fracture is found, conservative treatment should be chosen according to the condition. If a fracture is found, plaster fixation or surgery should be chosen according to the condition. 2. Septic osteomyelitis: Septic osteomyelitis is a suppurative infection of the bone and joints, which should be treated immediately with adequate antibiotics to fight infection, and commonly used drugs include cefoperazone, amoxicillin, etc. If localized antibiotics are used after 36 hours of treatment, the patient should be treated with antibiotics. If there is no obvious relief of local pain and swelling after 36 hours of antibiotic treatment, surgery should be performed as soon as possible, including drilling and drainage or open window decompression surgery. 3. Bone tumors: benign bone tumors are usually treated by surgical resection or scraping, and usually do not need adjuvant treatment after surgery, such as osteoid osteoma and osteochondroma. Malignant bone tumors are mainly treated with surgery as the main comprehensive treatment, after surgical resection of the tumor, according to the condition of the auxiliary chemotherapy or radiotherapy, such as osteosarcoma, Ewing’s sarcoma and so on. It is recommended to go to the hospital in time to improve X-ray film, CT, MRI and other related examinations, so as to clarify the cause of the disease in time, and to be treated accordingly.