Single-leg squat (SLS) is a test commonly used to assess lower limb function in rehabilitation. Increased hip adduction and internal rotation (IR) is associated with dynamic knee valgus, which is related to hip and knee overload. Proximal and distal factors, such as hip passive stiffness, poor hip muscle strength and excessive foot misalignment may influence hip movement. However, previous studies focus on how proximal and distal factors affected knee joint movement and did not reported the influence on hip joint. This study investigated the association of hip external rotators (ER) strength, hip passive stiffness and shank-forefoot alignment (SFA) with hip adduction and IR during SLS. Cross-sectional study. Forty-six health participants of both sexes (23.47 ± 4.29 years, 60.40 ± 11.28 kg, 1.67 ± 8.9 m) had SFA, hip ER torque, hip passive stiffness and hip kinematics assessed. Multiple linear regressions were performed to identify the factors which associated with mean and peak hip adduction and IR movement during SLS. Only hip passive stiffness was associated with mean (R2 = 0.164; Confidence Interval (CI) 95% = [-0.250, -0.048]; p = 0.005) and peak (R2 = 0.116; CI 95% = [-0.223, -0.210]; p = 0.019) hip IR movement. Hip passive stiffness was associated with mean and peak hip IR movement during the SLS. These results suggest that individuals with reduced hip passive stiffness may demonstrate increased hip IR movement during SLS.