Lower limb muscles’ thicknesses are weakly associated with dynamic knee valgus during single-leg squat in women with patellofemoral pain

Introduction Patellofemoral pain (PFP) patients often show an altered lower limb alignment during the single-leg squat (SLS). There is evidence that proximal and distal-to-the-knee muscle alterations can modify the lower limb alignment in PFP patients. However, we observed a lack of studies investigating the possible association between the thickness and strength of proximal and distal-to-the-knee muscles and lower limb alignment during SLS in women with PFP. Therefore, this study aimed to investigate the association between the thickness and strength of lower limb muscles and dynamic knee valgus (DKV) during SLS in women with PFP. Methods Cross-sectional study, where fifty-five women with PFP were submitted to the following evaluations: (1) muscle thickness (MT) of Gluteus Medius (GMed), Gluteus Maximus (GMax), Vastus Lateralis (VL), and Tibialis Anterior (TA); (2) isometric peak torque of hip abductors, hip external rotators, knee extensors, and foot inversors; and (3) DKV during SLS. Results There was a significant negative association between GMax's MT and DKV (r = −0.32; p = 0.01), and between TA's MT and DKV (r = −0.28; p = 0.03). No significant correlations were observed between isometric torques and DKV. Regression analysis found that GMax's MT explained 10% of the DKV's variance during SLS. Discussion Poor lower limb alignment during SLS is weakly associated with proximal and distal-to-the-knee muscle thicknesses, with no association with isometric torque in PFP women. Conclusion Our results suggest that other factors besides strength and muscle thicknesses may explain and improve lower limb alignment in women with PFP.