In a prospective study of 29 consecutive cases of tibial tubercle advancement, the patients were assessed on the Larson knee chart preoperatively, three years postoperatively, and again after a minimum of six years (range, six to eight years; mean, 7.2 years). Only one patient was lost to follow-up evaluation. The overall results show that at three years, 65.5% of the knees were excellent or good, 13.8% were fair, and 20.7% were poor. By six years a significant change occurred in five knees. Four knees deteriorated, while one improved. The remainder maintained their three-year postoperative grade. The patients provide clinical evidence to support the biomechanical and morphological observations that form the basis of the Maquet principle. Two considerations influence the final result: surgical complications (three out of four cases with complications had a poor result) and the preoperative status (in patellofemoral osteoarthritis a preoperative Larson score of over 60 is necessary for a satisfactory outcome).