Intra-articular osteoid osteoma in the proximal tibia and its imaging characteristics.

Due to mostly non-specific clinical symptoms and variable appearance on magnetic resonance imaging (MRI), the diagnosis of an intra-articular osteoid osteoma (iaOO) is often delayed. We report the case of a 26-year-old male with an atypical clinical manifestation of an iaOO in the proximal tibia and its MRI specific characteristics of tumor progression. The patient presented to our clinic after receiving multiple unsuccessful conservative and surgical interventions due to anterior knee pain, which persisted for 12months. Prior to the correct diagnosis of iaOO manifestation, the patient was subjected to multiple steroid infiltrations and two arthroscopies including partial meniscal resection. Due to increasing complaints, meniscal transplantation, bone decompression and/or ACL reconstruction were recommended. Subsequent computer tomography (CT) scanning and successful test medication with salicylates (ASS) confirmed iaOO presentation. Only after arthroscopic tumor resection was the patient symptom free at three months of follow-up. The present description of MRI specific characteristics of iaOO progression has the potential to accelerate correct tumor detection in the future.