This prospective randomized study compares the long term results between total knee arthroplasty with a mobile bearing high flex and a fixed bearing posterior stabilized knee (LPS) in 39 patients. The Hospital for Special Surgery score (HSS) was calculated and radiographs in AP and lateral view were analyzed after a minimum follow-up of 10 years. No significant differences between the two groups were found. The mean HSS-score was 90.67 (+/- 5.75) for LPS group patients and 90.83 (+/- 8.57) points for the high flex group patients. Three patients in the high flex group had undergone a reoperation on their knee. One knee was revised for painful mid-flexion instability and the others for symptomatic aseptic loosening of the tibial prosthesis. Based on these and other findings, the use of a high flex knee system may be seriously re-considered. Further studies are required to evaluate possible long-term adverse effects of high flex knee systems.