Thirty-three patients had an arthrodesis of the knee by means of an intramedullary nail introduced through the greater trochanter. Fifteen of the procedures were done for a failed knee arthroplasty; eight had failed because of infection and seven, because of aseptic loosening. Twenty-nine of the thirty-three knees united three to four months after the first attempt at arthrodesis and three united after technical errors were corrected. One knee had a broken nail and a non-union; this was still untreated at the time of writing. Four nails broke: three in the line of fusion and one in the line of an infected supracondylar pseudarthrosis of the femur. No new infections developed after the arthrodesis. Three patients had had an infection and a chronic fistula before the arthrodesis, and the fistulae healed six, fourteen, and eighteen months postoperatively. In another patient, who had had infection and necrosis of the skin preoperatively, the wound healed in six months. All of these knees healed without an additional major operation. The functional result was satisfactory in all patients. After the arthrodesis, seventeen of the thirty-three patients needed less aid when walking, and no patient needed more aid. Fusion of the knee with a long intramedullary nail can be safe and effective, even in the presence of infection, if the revision is performed properly and certain technical principles are followed. It is especially important to establish good contact between the resected bones.