A 54 year old man presented to the emergency department with an acutely locked left knee. He had had a unicondylar knee replacement done on this knee 18 months earlier. Plain x rays were taken (fig 1A) which confirmed the dislocation of the meniscal bearing. An attempt to reduce the knee under sedation in the emergency department was unsuccessful and an orthopaedic consultation was requested. An attempted manipulation under anaesthetic to reduce the …