The purpose of this study is to measure the outcomes of patients who have articular cartilage lesions in the patellofemoral joint and are treated with the Autologous Chondrocyte Implantation.

Cartilage restoration, in general, is a relatively new option for the treatment of articular cartilage lesions primarily of the knee. In the initial autologous cultured chondrocyte transplantation (ACT or, by others implantation, thus ACI) reported by Peterson et. al., the results of femoral lesions were favorable, while 5 of 7 patellofemoral treatments were poor. In the United States, the expedited FDA approval based on these results excluded the patella. As a result, in the United States, it has been difficult to further evaluate use of ACI at the patellofemoral joint in light of the exclusion of "off label" uses by many governmental and private insurance programs. Nevertheless, a growing body of knowledge is accumulating outside the United States that the use of ACI at the patella is a viable option and soon similar findings will be published in the US by Minas et. al. (accepted for publication)

Inclusion Criteria:

• Carticel Implantation of the patella and/or trochlear lesion. Patients who have reached their two-year follow-up date. All patients included in sequential order.

Exclusion Criteria:

• Patients that have had a microfracture in the knee joint at the same time as Carticel Implantation.

Patients that have implantable lesions other than the patella and trochlea.