[Osteoid osteoma of the lower end of the femur--a diagnostic problem]

Joint symptoms may be the first manifestations of juxta-articular osteoid osteoma; therefore, diagnosis may be difficult. We report the case of a young athlete who presented an osteoid osteoma of the distal part of the femur. Correct diagnosis was delayed by the presence of a pathological mid-patellar plica synovialis and the absence of modifications on standard X-rays.