Intraarticular osteoid osteoma of the knee misdiagnosed as meniscal tear: a case report

INTRODUCTION Osteoid osteoma is a relatively frequent benign boneforming tumor that accounts for about 5% of all bone tumors and 11% of benign bone tumors. It mostly involves the long bones of the appendicular skeleton and is characterized by episodes of night pain. Although nonsteroidal antiinflammatory drugs (NSAIDs) generally reduce the pain, such treatment requires long-term (3 to 4 yr) consumption of those medications. Surgical excision is indicated for patients with severe pain that is nonresponsive to medications. CT scanning is the modality of choice for the diagnosis of osteoid osteoma to show the characteristic nidus. The diagnosis is not generally difficult if the typical clinical and radiographic features are present. However, in a considerable number of patients, the lesion is not presented with typical characteristics, making the diagnosis difficult. For that reason, misdiagnosis of osteoid osteoma occurs frequently. In one study, 44.8% of patients with osteoid osteoma were misdiagnosed with other lesions such as intraarticular infection, synovitis, Perthes disease, osteomyelitis, and joint tuberculosis. Intraarticular localization of osteoid osteoma accounts for about 10% of those lesions and is associated with nonspecific pain and symptoms that generally are misdiagnosed with more common joint pathologies, such as inflammatory joint diseases or osteochondritis dissecans (OCD). For that reason, its diagnosis has been made with a significant delay compared to extraarticular lesions (26.6 mo vs. 8.5 mo). Since misdiagnosis could lead to overtreatment of the patient as well as long-term patient suffering, awareness of conditions that may complicate the diagnosis of osteoid osteoma is critical. This study reports a complicated diagnosis of intraarticular osteoid osteoma in an adult female who presented with persistent knee pain. Informed consent was obtained from the patient to use her medical data for publication. Case reports do not require ethical approval according to the guidelines of the authors’ university. CASE REPORT