Subcutaneous joint-mouse escape during knee-joint arthroscopy.

During arthroscopy of the knee, large volumes of fluid are required. Cadaver studies have indicated that flexion of the knee may cause rupture of the joint capsule during arthroscopy. To illustrate this, a rare case is presented with rupture of the posterior part of the capsule during arthroscopy with extrusion of a joint mouse. This possibility should be considered when the joint mouse cannot be found inside the joint during arthroscopy.