Medial compartment knee osteoarthritis (OA) is strongly associated with varus malalignment, which shifts the mechanical axis medially increasing loads in the medial tibiofemoral compartment and accelerating cartilage degeneration. Musculoskeletal modeling provides a non-invasive method to estimate knee contact forces (KCFs) and muscle forces, supporting biomechanical analysis and clinical decision-making. Previous research at the Istituto Ortopedico Rizzoli focused on geometric personalization of knee models (tibiofemoral angle (TFA) and contact point (CPs) location), and started to explore the effects of subject-specific muscle insertions. However, the influence of muscle insertions on predicted KCFs and muscle forces remains unclear. In particular, no studies have systematically examined its impact on the distribution of medial contact forces (MCF) and lateral contact forces (LCF).