Background: Total knee replacement (TKR) is a surgical procedure for intractable degenerative disease of the knee joint. Despite continued evolution in prosthesis design and surgical procedures, restricted range of motion and functional performance is still common in patients undergoing TKR. Posterior stabilized TKR aims to maintain a more reproducible roll back than cruciate retaining and mobile bearing knees, possibly leading to better flexion and function.The aim of this study was to compare the performance of De-Puy posterior-stabilized rotating platform TKR prosthesis (PS-RP) with the newer Hi-Flex PS-RPF system. In particular, the two prostheses were compared for patient satisfaction and functional outcome.Methods: Seventy physically active patients with unilateral knee osteoarthritis, allocated for primary TKR were recruited into the study. Patients were randomly allocated to one of the two treatment groups. The pre and post-operative data (functional outcome and patient satisfaction) was statistically analysed between the two groups.Results: There were no statistical subjective differences between the 2 groups at 6 weeks and 12 months post-operative. There was a significant difference between knee flexion of patients in the Hi-Flex TKR group at 12 months post-operative, achieving higher mean flexion (123.8 ± 7.8 deg compared to 116.4 ± 14.1 deg; p < 0.013). However, this group also had better preoperative flexion suggesting direct correlation between the preoperative and postoperative knee flexion angles, in keeping with current literature. Conclusion:Therefore, we concluded that there are no significant subjective or objective differences between hiflex and standard knee replacements after 12 months of follow-up.