Effect of Q-angle symmetry on knee joint kinematics in level walking, upslope walking and landing task

BACKGROUND: The quadriceps angle (Q-angle) is a key biomechanical measure of lower limb alignment. While its asymmetry is linked to knee disorders like patellofemoral pain, its dynamic impact on full six-degree-of-freedom (6DOF) knee kinematics across different tasks remains unclear. METHODS: Forty healthy university students were categorized into Q-angle symmetric (QS, bilateral difference ≤ 3°) or asymmetric (QA, > 3°) groups. Knee 6DOF kinematics were captured during level walking, 10% upslope walking, and landing task using a 3D motion capture system. The International Physical Activity Questionnaire (IPAQ), Visual Analogue Scale (VAS) for pain, and Kujala score were assessed at baseline and 18-month follow-up. Statistical parametric mapping (SPM1D) was used for kinematic analysis. RESULTS: During level walking, the QA group showed greater internal rotation at 69-74% gait cycle (GC) (p = 0.042) and altered flexion/extension at 75-90% GC (p = 0.012). During upslope walking, the QA group exhibited different flexion/extension at 74-87% GC (p = 0.018). No kinematic differences were found in any 6DOF parameter during landing task. At 18 months, there were no significant intergroup differences in IPAQ, VAS, or Kujala scores (all p > 0.05). CONCLUSION: Q-angle asymmetry induces task- and phase-specific alterations in knee angular kinematics during walking tasks but does not affect translational kinematics or short-term functional outcomes in healthy young adults. Its biomechanical effect is limited and context-dependent, suggesting caution in using it as a standalone risk marker for knee injury.