Intra-articular osteoid osteoma simulating a painful fabella syndrome.

We present a case of an intra-articular osteoid osteoma in the knee that was mistaken for a painful fabella syndrome after unsuccessful knee arthroscopy for the treatment of postero-lateral knee pain. In this case both the initial clinical presentation and the imaging proved to be deceiving. The diagnosis of intra-articular osteoid osteoma was considered only once typical clinical features appeared and a Computerized Tomography scan was performed. We discuss the difficult of diagnosing an intra-articular osteoid osteoma and the imaging of choice.