New insert types have been developed to improve clinical and functional outcome in mobile bearing (MB-TKA) and fixed bearing total knee arthroplasty (FB-TKA). A prospective single blinded randomised controlled clinical trial was performed to evaluate 2 types of MB-TKA inserts and 2 types of FB-TKA inserts of the Genesis II prosthesis (Smith & Nephew) in 146 patients with 5-years follow-up. A significant difference (P= .042) between the MB-TKA inserts was found in KSS function scores, but clinical significance is expected to be limited. Goniometry, temporal gait parameters and QoL were similar in all groups. Survival was significantly better (P= .047) for FB-TKA. The comparable outcome and higher revision rate in MB-TKA indicate that FB-TKA may be preferential for the Genesis II implant system.