Reported results for patellar ACI include a mixed population of patients having or not a concomitant correction of the extensor mechanism. No study has reported separate outcome for those two patellar ACI subgroups. Forty four patients were included in this study designed to compare the outcome of patellar ACI with extensor realignment (group A) to patellar ACI with normal patellofemoral tracking (group B). Group A (n=22) had a higher increase in average modified Cincinnati knee score (4.5 vs. 1.7 points), better function (1.7 vs. 2.5), better SF-36 physical component scores (70.9 vs. 55.4 points) and higher IKDC scores (85.2 vs. 60.6 points) when compared to group B (n=22) at an average follow-up of 2 years. Patellar ACI with concomitant extensor realignment has superior outcome than patellar ACI with normal patellofemoral tracking. An unloading osteotomy could be desirable in selected patients with normal patellofemoral biomechanics to improve the outcome in this population.