We compared the early results of mobile-bearing knee prosthesis with fixed-bearing knee prosthesis in 16 patients who had one-stage, sequential, bilateral replacements. In each patient, a Low Contact Stress (LCS, Depuy) rotating-platform prosthesis was inserted in one side, and an Anatomic Modular Knee (AMK, Depuy) posterior-stabilised prosthesis was inserted in the other side. The same surgical routines were adopted for both sides in each patient. There were significant improvements in the Knee Society knee score and functional score, as well as the Oxford Knee score after both mobile-bearing and fixed-bearing knee replacements (p<0.001). However, we could not find any significant difference between the clinical results of the two prostheses. The authors early experience with the mobile-bearing total knee prosthesis was as favourable as the medium-term experience of the fixed-bearing total knee prosthesis in this prospective, match-pair study.