Knee frontal (adduction/abduction) and sagittal (flexion/extension) moments have been implicated in the pathomechanics of knee osteoarthritis (OA). The aim of this study was to evaluate the change in the knee sagittal moment in a cohort of patients with knee OA undergoing a biomechanical training program. Twenty-five female patients with symptomatic medial compartment knee OA were enrolled in a customized biomechanical intervention program. All patients underwent consecutive gait analyses prior to treatment initiation, and after 3 months and 9 months of therapy. Self-evaluative questionnaires, spatiotemporal gait parameters, peak knee sagittal moments, knee sagittal impulses, and duration of knee moments were compared throughout the duration of therapy. Differences between baseline and follow-up values were examined using nonparametric tests. Peak knee flexion moment (KFM) at loading response decreased significantly with therapy (p = 0.001). Duration of KFM and impulse of knee flexion also decreased significantly (p = 0.024 and p = 0.029, respectively). These changes were accompanied by increased walking velocity, significant pain reduction, and increased functional activity. Post-training kinetic evaluation demonstrated profound alterations of knee sagittal moments at the loading response KFM. We speculate that knee sagittal moments can potentially be improved in patients with knee OA over time with a biomechanical training program.