Background:It has been hypothesized that mobile-bearing total knee arthroplasty (TKA) may enhance outcomes by accommodating femorotibial rotational mismatches, potentially lowering contact stresses and reducing polyethylene wear. This study aimed to evaluate whether a difference exists between fixed-bearing and mobile-bearing designs of a modern TKA in terms of durability, range of motion (ROM), and functional outcomes at 5 years postoperatively. Materials and Methods: This comparative analysis included 278 patients who underwent primary cemented TKA with one of three tibial components: all-polyethylene fixed-bearing, modular metal-backed fixed-bearing, or mobile-bearing. The median follow-up was 5 years (IQR: 3–8 years). Results:No significant difference was observed in durability, assessed by survivorship free of revision for any cause, or in mean maximal ROM at ten years. Functional outcomes, as evaluated by Knee Society (KS) function scores and the prevalence of patellar tilt, also showed no significant differences between the groups. Conclusion:This clinical study demonstrated that the mobile-bearing TKA design is reliable and durable but does not offer superior maximum knee flexion, functional outcomes, or durability at 5 years compared to posterior-stabilized fixed-bearing designs utilizing either all-polyethylene or modular metal-backed tibial components.