Effects of hip stability training versus standard care on Q-angle and pain in marathon runners with patellofemoral pain syndrome: A retrospective cohort study

OBJECTIVE: Hip stability training may influence the quadriceps angle (Q-angle) and pain, but the clinical relevance of static Q-angle changes remains uncertain. This study compared hip stability training with standard care for Q-angle, pain, and function in marathon runners with Patellofemoral Pain Syndrome (PFPS). METHODS: We identified 487 marathon runners with PFPS, of whom 312 met the eligibility criteria. After 1:1 propensity score matching, 94 runners were retained in each group: hip stability training (Hip-STAB) and standard care (Control). Outcomes were assessed at baseline (W0) and at 4, 8, and 16 weeks (W4, W8, W16). Primary outcomes were standing Q-angle, visual analog scale pain during running (VAS-Run; 0-100 mm), and Anterior Knee Pain Scale (AKPS; 0-100 points). RESULTS: Both groups improved over 16 weeks. Linear mixed-effects models showed significant time effects for Q-angle, VAS-Run, and AKPS (all p < 0.001), but no significant time-by-group interactions for Q-angle (p = 0.190), VAS-Run (p = 0.302), or AKPS (p = 0.317). Bonferroni-adjusted post-hoc comparisons did not identify significant between-group differences at W16. The association between Q-angle reduction and VAS-Run improvement was significant in the Hip-STAB group (r = 0.35, 95% CI 0.16 to 0.52, p < 0.001) and the Control group (r = 0.44, 95% CI 0.26 to 0.59, p < 0.001). CONCLUSIONS: Hip-STAB and standard care were each associated with improvements in static Q-angle, running pain, and function, but Hip-STAB was not superior to standard care. The correlation between Q-angle and pain changes should be interpreted as an association rather than evidence of a causal biomechanical mechanism.