Sex differences in factors of pelvis and lower-limb joint kinematics influencing dynamic knee valgus during single-leg squat

BACKGROUND: Dynamic knee valgus (DKV) during dynamic activity is associated with patellofemoral pain, one of the most common sports disorders, especially in females. No studies have examined the factors that can lead to DKV in females as compared to males while addressing the influence of factors on each other. OBJECTIVE: To identify factors of pelvis and lower joints kinematics affecting DKV during single-leg squat (SLS) in females compared to males with multiple regression analysis. METHODS: Forty-four healthy young people (24 females, 20 males) performed SLS, and pelvis, hip, knee, and ankle 3D kinematics were recorded. The 2D knee frontal plane projection angle (FPPA) was adopted as the DKV measurement. Multiple regression analysis was performed to determine the relationship between FPPA and the kinematics of each joint and segment. RESULTS: Hip adduction and pelvic contralateral rotation were explanatory factors for FPPA in females. Hip adduction, hip internal rotation, and knee external rotation were explanatory factors in males. CONCLUSIONS: The lower limb or pelvic motion factors affecting DKV during SLS differ between the sexes, with pelvic contralateral rotation being extracted only in women, possibly due to differences in pelvic width.