Subperiosteal Osteoid Osteoma of the Knee: Case Report

Osteoid osteoma is a benign osteoblastic bone tumor that is usually encountered in adolescent and young adult males (1). The typical findings of osteoid osteoma in a long tubular bone are the presence of a small, well-defined radiolucent lesion with or without mineralization within the cortex, associated with cortical thickening and reactive sclerosis (2). Osteoid osteomas can be categorized according to its location in the bone; subperiosteal, intracortical, endosteal, or intramedullary (2). Subperiosteal form may produce atypical radiological features, and thus, in more than half of reported cases, the first diagnosis was wrong (3). Few reports have been issued on subperiosteal osteoid osteoma, and the majority of reported images are radiographs or gross photographs. Here, we describe an unusual case of subperiosteal osteoid osteoma without reactive cortical thickening occurring in the distal femur and its radiographic, computed tomography (CT), ultrasonographic (US) and magnetic resonance imaging (MRI) characteristics. This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/ by-nc/3.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited. Received: December 30, 2015 Revised: March 24, 2016 Accepted: March 25, 2016