The results of partial patellectomy as a treatment for displaced patellar fractures were assessed retrospectively with use of clinical, radiographic, and isokinetic strength-testing criteria. Forty patients who had been followed for an average of 8.4 years were studied. In the extremity that had been operated on, the mean active range of motion was 94 per cent, the circumference of the thigh was 100 per cent, and the strength of the quadriceps was 85 per cent of these measurements in the contralateral extremity. The over-all result was rated as excellent in twenty patients, good in eleven, fair in six, and poor in three. There was a significant statistical correlation between the type of fracture and the outcome. The results of this study indicate that partial patellectomy can be an effective treatment for selected patellar fractures.