Background: In recent years, decisions regarding the treatment of individual patients have increasingly been affected by economic considerations. The G-DRG system reimburses sledge endoprosthetic implantations at a much lower rate than surface replacements and at significantly different cost weights (CW). Therefore, when only G-DRG payments are considered, TKA produces higher gains. Taking only these revenues alone into consideration, however, does not provide the basis of an economically sound decision-making process. The target of this research was to present a comparison between variable costs of the two procedures. Methods: The mean cost and performance data of 28 Endo-Modell (Link company) sledge implantations (UKS) and of 85 NexGen CR surface replacement total knee arthroplasties (TKA; Zimmer company) were compared in 2007. Results: From the perspective of the hospital, UKS treatment is of greater economic advantage when the medical indication is given. In preferring UKS marginal contribution can be improved, and although the relative weighting is comparatively low, the costs are significantly lower than in a comparative analysis of TKA. Based on the length of stay required for each procedure the average daily CW for UKS can be calculated as 0.1728, while being 0.1955 for TKA. The earlier release of the first patient results in another patient being admitted 1.5 days earlier and thus an increase in case mix. Meanwhile, the case-mix index and the costs of care per case decrease ceteris paribus. Conclusion: Assuming the correct medical indication, the hospital seeking to maximize its marginal contribution would be wise to select sledge endoprosthesis implantation. Considering the economic perspective of gains and costs, the assumption that TKA is advantageous could not be confirmed in the present study.