Abstract <p>This study evaluates the effects of affordable back spring-loaded knee braces on lower-body joint kinematics and upper leg muscle activity during treadmill walking at 3, 5, and 7 km/h. With 30 male adult participants, using IMU-based motion capture and surface electromyography (EMG), joint trajectories of the knee, hip, and ankle in frontal, sagittal, and transverse planes were analyzed using both multivariate (PCA-based) methods, which capture inter-joint coordination, and univariate (paired) methods, which treat each joint or muscle variable independently. Results revealed that knee bracing systematically restricted knee flexion/extension, abduction/adduction, and internal/external rotation, up to 37.8% during the swing phase at slow speeds. Hip and ankle movements were also affected, indicating compensatory adjustments to maintain pace or balance. PCA-based analysis showed that brace effects were most pronounced at moderate speeds (5 km/h), and joint coordination patterns were significantly altered (<InlineEquation ID="IEq1"> <EquationSource Format="TEX">\(p &lt; 0.001\)</EquationSource> </InlineEquation>). Paired analysis showed consistent decreases in knee range of motion (ROM) and earlier peak flexion timing, despite the fact that muscle activity changes were minor and did not survive multiple-comparison correction. Although further studies may be required in elderly patients to generalize the findings, the results suggest that back-spring-loaded affordable knee braces can effectively stabilize the knee, albeit their use induces speed and phase-dependent compensations at the hip and ankle joints. Therefore, clinicians should weigh the benefits of knee stabilization against potential gait alterations when recommending such braces.</p> Graphical abstract <p></p>