Valgus bracing reduces cartilage mechanical responses in knees with varus malalignment and medial osteoarthritis: A neuromusculoskeletal-finite element analysis.

Valgus bracing is a common intervention aiming to reduce medial knee compartment loading in individuals with varus malaligned knees and medial knee osteoarthritis (KOA). However, its effects on cartilage mechanics relevant to tissue health and failure remain unknown. We investigated whether valgus bracing reduced cartilage surface stresses and strains, and thus potential risk for further cartilage degradation, in individuals with knee varus malalignment and medial KOA. Twenty-two participants (Kellgren-Lawrence grade ≥ 2) completed unbraced and braced walking trials. Participant-specific knee geometries from magnetic resonance imaging were implemented in a validated 12-degree-of-freedom knee model and combined with electromyography-informed neuromusculoskeletal simulations to estimate tibiofemoral kinematics and kinetics. These outputs were applied to finite element models, where participant-specific femoral and tibial cartilage geometries were implemented and modeled as fibril-reinforced poroviscoelastic materials and menisci as fibril-reinforced poroelastic materials. Maximum principal stress, maximum shear strain, and collagen fibril strain were quantified on medial and lateral tibial cartilages. Although responses varied widely across participants, valgus bracing reduced medial tibial cartilage stress and strain during the second peak of ground reaction force (70-90% stance phase) in individuals with higher knee varus angles. For example, the group-average maximum principal stress in the medial compartment decreased by 9.3% (p = 0.01). These findings indicate valgus bracing alters cartilage mechanical responses, associated with the risk of tissue degeneration, in some individuals with medial KOA and varus malalignment. The results highlight the influence of individual biomechanics and support personalized bracing strategies.