On closer questioning, the child seems to have had pain in the area for a few weeks or longer. Precisely when the pain began is difficult to pin down. There is no history of injury when the pain actually began a few weeks ago. There are no contributing past medical, surgical, social, or familial factors. On examination, the patient is afebrile, and in no acute distress. There is limping, antalgic gait and station. Examination of the leg shows the area is slightly warm and slightly tender. There is no redness. There is no irritability of the knee or of the ankle. The neurologic status of the foot and the pulse in the foot are normal. The hip range of motion is normal. There is no regional or central lymphadenopathy. I instructed the father to give the patient Naprosyn, and monitor his response. The patient had minimal relief of pain from the Naprosyn. Biopsy was performed and histopathology is shown. Radiographs show a lesion in the mid tibia, within the medullary cavity.There is slight expansion of the cortex, with thinning. There appears to be a faintly calcified matrix. A bone scan shows abnormal uptake, and a CT scan shows the lesion in better detail.