Intra-articular foreign body after arthroscopy.

We report a case of a small metal fragment that dissociated from an arthroscopic instrument and remained inside the knee joint for 14 months, causing recurrent swelling and pain. For safety reasons, arthroscopic instruments should be checked carefully at the end of surgical procedures because the loss of the fragment was not obvious and the device was still functioning. To our knowledge, this is the first case of an undetected foreign body iatrogenically introduced into a joint by arthroscopy.