A prospective, randomized comparison of posterior cruciate-retaining (PCR) and posterior stabilized (PS) total knee arthroplasties (TKAs) was conducted in 20 patients who underwent bilateral TKAs for osteoarthritis. All procedures were performed by a single surgeon. One knee was implanted with a PCR TKA, and a contralateral knee with a PS TKA. Both prosthetic designs were of the same TKA series, with comparable surface geometries. Patients had a clinical and radiographic evaluation at a mean of 31.7 months for PCR TKAs and 30.6 months for PS TKAs postoperatively. There were no significant differences between the PCR and PS TKAs in postoperative knee scores. However, postoperative improvement in range of motion was significantly superior in the PS group.