Gait pathomechanics in early-stage knee osteoarthritis: do non-traumatic and post-traumatic patients walk differently?

Altered knee joint loading in early-stage osteoarthritis may accelerate cartilage degeneration and symptom progression. This cross-sectional observational study investigates differences in knee joint pathomechanics between 22 patients with early-stage post-traumatic knee osteoarthritis (PTOA), 26 patients with early-stage non-traumatic knee osteoarthritis (NTOA) and 20 age-/gender-matched healthy controls. Participants walked barefoot at self-selected speeds while marker data (100 Hz), ground reaction forces (1000 Hz), and surface electromyography (1000 Hz) were recorded. electromyography-informed musculoskeletal simulations estimated knee contact forces (KCF) and joint mechanics. Group differences in these outcomes and measured muscle activations were assessed via Statistical Parametric Mapping t-tests. Analysis of Covariance investigated the influence of covariates (age, gender, gait speed, alignment, strength). Early-stage NTOA and PTOA patients exhibit similar KCF and joint mechanics. Both patient groups exhibited significantly reduced second KCF peaks compared to controls (p = 0.019, Δmean NTOA - controls = 1.07 BW, Δmean PTOA - controls = 0.98 BW), suggesting knee underloading, in contrast to the joint overload typically seen in established OA. Additionally, gait speed significantly influenced KCF peaks. These findings suggest that early OA may be characterized by cartilage underloading. Longitudinal studies and more demanding tasks may reveal phenotype-specific biomechanical distinctions and also confirm continuous cartilage underloading in disease progression.