Background and Objectives: Total knee arthroplasty (TKA) is one of the most common medical procedures worldwide. However, 10 to 20% of patients are still dissatisfied despite implants and surgical technique advancements. Recently, several medial-stabilized TKAs have been developed in attempts to replicate the native kinematics of the knee. The aim of this scoping review on medial-stabilized TKA inserts—medial congruent (MC) and medial pivot (MP)—is to focus on their clinical outcomes and the role of the posterior cruciate ligament (PCL), aiming to systematically map the existing research and highlight current knowledge gaps. Materials and Methods: A search of the PubMed, Embase and Cochrane databases was performed to identify relevant studies on the kinematics and outcomes of medial pivot (MP) or medial congruent (MC) inserts. The following Mesh terms were used in combination with the Boolean operators “AND” and “OR”: “total knee arthroplasty”, “total knee replacement”, “medial pivot”, “medial congruence”, “outcomes” and “kinematic”. Original studies reporting on clinical outcomes assessed with validated patient-reported scales, surgical techniques and reoperation rates for any reason with a minimum follow-up of 18 months were included. Results: A total of 39 articles met the inclusion criteria, accounting for 6143 total knee replacements. The overall reoperation-free survivorship rate was 98.4% (6047 out of 6143 knees) at a weighted average follow-up of 6.3 years (range 1.5–15.2 years, SD 0.7). Both MP and MC inserts demonstrated good outcomes, with no differences between groups. Few studies evaluated the role of the PCL in MP and MC inserts, with no differences in terms of clinical outcomes between retaining and sacrificing the PCL. Conclusions: MS-TKA demonstrated good outcomes in the literature independently of the specific design (medial pivot or medial congruent). Different possible biases may be present when evaluating the outcomes of these inserts, including different types of alignment and soft tissue balancing philosophies.

Purpose: Few studies in the literature have evaluated the effect of weight changes on knee joint biomechanics induced by total knee arthroplasty (TKA). The aim of this study was to evaluate changes in the hip muscular moment and the thigh centre of mass following primary TKA. Methods: All primary TKAs performed with conventional instrumentation between April and December 2024 were prospectively included. Radiographic measurements were obtained to develop an analytical biomechanical model. The resected bone was collected and weighed intraoperatively, together with the femoral component and implanted cement. An analytical biomechanical model was developed to estimate changes in thigh weight, centre of mass position and hip muscular moment before and after TKA. Results: A total of 70 patients were included in the study. Primary TKA resulted in a statistically significant increase in thigh weight and a distal shift of the thigh centre of mass ( p < 0.05). The average increase in implant‐related knee weight after TKA was 333.5 g (standard deviation [SD] 51.0 g), while the femoral weight increased by 199.1 g (SD 40.1 g), resulting in an average increase in total thigh weight of 2.8% (SD 0.6%; range: 1.6–4.2%). The analytical biomechanical model showed a statistically significant distal shift of the thigh centre of mass of 6.4 mm (SD 1.5 mm; range: 3.7–9.7 mm) after TKA ( p < 0.05). This redistribution of thigh mass was associated with a statistically significant estimated increase in hip muscular moment of 6.3% (SD 1.4%; maximum increase 9.3%; p < 0.05). Conclusion: Primary TKA alters thigh mass distribution through an increase in limb weight and a distal shift of its centre of mass. Within the assumptions of this analytical model, these changes result in an increase in estimated hip muscular moment. Further biomechanical and clinical studies are needed to determine the clinical relevance of these theoretical findings. Level of Evidence: Level IV.