The Strengthening of Quadriceps, Abductors, and External Rotator Muscles of the Hip to Alter Axial Alignment of the Lower Limbs in University Students with Patellofemoral Pain Syndrome: A Prospective Cohort Study.

Background: Proximal lower-extremity muscle strengthening is an important conservative intervention for patellofemoral pain syndrome (PFPS), as these muscle groups play critical roles in femoral stabilization and knee valgus control. However, evidence remains limited regarding the effectiveness of muscle strengthening in improving lower-extremity axial alignment through modulation of femoral neck anteversion, femoral internal rotation, and tibial external rotation. Therefore, the present study aimed to determine whether a strengthening protocol targeting the quadriceps and hip external rotator and hip abductor muscles could improve knee alignment and reduce bone torsion in young adults with patellofemoral pain syndrome. Methods: This prospective interventional cohort study implemented a muscle strengthening protocol in ten university students with PFPS. Outcomes included femoral neck anteversion angle (FNA), tibial tubercle-trochlear groove distance (TT-TG), tibial external torsion angle (TET), and the knee Q-angle, assessed via 3D reconstruction of computed tomography (3D-CT) images. Pre- and post-intervention data were analyzed using the Shapiro-Wilk test for normality and repeated-measures ANOVA (p < 0.05; 95% confidence interval). Results: Muscle strengthening improved lower-limb axial alignment, with reductions observed across all measures post-intervention. Mean changes were 0.68 ± 1.26° for FNA (p = 0.0626); 1.51 ± 0.97 mm for TT-TG (p = 0.0001); 1.38 ± 3.36° for TET (p = 0.2231); and 1.14 ± 1.52° for the Q-angle. Statistically significant improvements were observed for TT-TG and the Q-angle. Conclusions: Proximal muscle strengthening improved knee valgus and axial lower-limb alignment, as evidenced by significant reductions in Q angle and TT-TG distance. Reductions in femoral neck anteversion (FNA) and tibial external torsion angle (TET) were observed. However, these differences were not statistically significant. These findings support muscle strengthening as a noninvasive strategy for improving lower-limb alignment in individuals with patellofemoral pain syndrome.