Background: Genu varum may alter frontal-plane knee kinematics by changing lower-limb alignment; however, the knee response to treadmill incline in individuals with genu varum remains unclear. Therefore, this study aimed to investigate the effects of treadmill incline on mean knee angle and range of motion (ROM) during walking and running in individuals with genu varum and healthy controls.
Methods: In this quasi-experimental repeated-measures study, 36 young men (18 with genu varum and 18 healthy controls) performed walking at 1.3 m/s and running at 3 m/s on a treadmill at 0%, 5%, and 10% inclines. Knee kinematics were recorded using a three-dimensional motion analysis system, and mean knee angle and frontal-plane ROM were calculated. Data were analyzed using mixed analysis of variance.
Findings: Compared with healthy controls, individuals with genu varum showed a greater mean knee angle toward varus (p=0.005) and greater ROM (p<0.001). ROM was greater during running than walking (p=0.002) and decreased with increasing incline (p<0.001). In the genu varum group, ROM showed a significant linear decrease with increasing incline (p=0.003). The effect of incline on mean knee angle and the interactions among group, activity, and incline were not significant (p>0.05).
Conclusion: Increasing treadmill incline up to 10% was associated with reduced frontal-plane knee ROM without increasing mean knee angular deviation toward varus. The kinematic response to incline did not differ significantly between groups. As kinetic variables and joint loading were not assessed, no conclusions can be drawn regarding the mechanical safety or suitability of inclined treadmill exercise.