Chronic Osteomyelitis Mimicking Osteosarcoma in a Young Adult: The Role of Imaging

We report the case of a 19-year-old patient admitted to the trauma department with an inflammatory swelling of the right knee that had been evolving for three months. The clinical context and the aggressive appearance of the bone lesion initially suggested an osteosarcoma. However, imaging studies — ultrasound, CT, and MRI — revealed features suggestive of chronic osteomyelitis. Blood work showed signs of inflammation. Cytobacteriological analysis of the aspirated pus was sterile but showed a hemopurulent aspect rich in neutrophils. The definitive diagnosis of active chronic osteomyelitis was confirmed by bone biopsy. The patient was treated medically with a favorable outcome. This case highlights the importance of an integrated clinical and radiological approach to distinguish bone infections from malignant tumors, thereby avoiding inappropriate treatment.