The effects of forefoot varus on hip and knee kinematics during single-leg squat

Foot misalignments, such as forefoot varus (FV), have been associated with musculoskeletal injuries in the proximal joints of the lower limb. Previous theories suggested that this association occurs because FV influences knee and hip kinematics during closed kinetic chain activities. However, research on the effects of FV in the kinematics of the lower limb is very scarce. Therefore, the purpose of this study was to compare the knee and hip kinematics between subjects with and without FV during a functional weight-bearing activity. Forty-six healthy adolescents were divided into two groups: group of subjects with FV (VG, n = 23) and group of subjects with aligned forefoot (CG, n = 23). A kinematic evaluation was conducted while the subjects performed a single-leg squat task. The variables of interest were hip internal rotation and adduction and knee abduction excursions at 15°, 30°, 45° and 60° of knee flexion. Between-group comparisons were performed with multivariate analysis of variance. Results showed that the VG presented greater hip internal rotation when compared with the CG across all evaluated knee flexion angles (P = 0.02-0.0001). No differences between groups were observed in hip adduction or knee abduction (P > 0.05). These results indicate that FV influences the transverse plane hip movement patterns during a functional weight-bearing activity. Considering that excessive hip internal rotation has been associated with knee injuries, these findings might contribute for a better understanding of the link between FV and injuries of the proximal joints of the lower limb.