We performed a retrospective study of the results of proximal tibial osteotomy in thirty-four men (thirty-seven knees) who had had unicompartmental osteoarthrosis of the knee. The average age of the patients at the time of the procedure was forty-nine years (range, twenty-eight to sixty years). The functional results were evaluated according to the system of Tegner and Lysholm, in which the level of participation in work and sports activities is graded on a scale from 0 points (complete disability) to 10 points (the ability to participate in competitive sports at the elite professional level). The average functional score was 5.4 points (range, 2 to 8 points) preoperatively and 4.8 points (range, 1 to 8 points) postoperatively. Postoperatively, many of the patients were able to participate in activities, such as running and jumping, that can lead to damage of the components of a total knee arthroplasty. Twenty-eight (82 per cent) of the thirty-four patients stated that the results had met their expectations and that they would have the operation again given the same situation.