A comparison of the clinical and radiographic results of patients with metal-backed monoblock Insall-Burstein I and modular Insall-Burstein II Posterior Stabilized Knee Prostheses was done. The minimum followup was 10 years. The clinical results were comparable with a similar average Hospital for Special Surgery knee score of 85 and 84 points, respectively. Likewise, the Knee Society Knee and Functional Scores showed no statistical difference. Radiographically, the incidence of minor radiolucent lines was 11% for the Insall-Burstein I prostheses and 29% for the Insall-Burstein II prostheses, but their presence was of no clinical significance. There was no clinical or radiographic evidence of tibial component loosening with either prosthetic design and there were no revisions for polyethylene wear or osteolysis in either cohort of patients.