Coupling motion between rearfoot and hip and knee joints during walking and single-leg landing

The objective of the current study was to investigate the kinematic relationships between the rearfoot and hip/knee joint during walking and single-leg landing. Kinematics of the rearfoot relative to the shank, knee and hip joints during walking and single-leg landing were analyzed in 22 healthy university students. Kinematic relationships between two types of angular data were assessed by zero-lag cross-correlation coefficients and coupling angles, and were compared between joints and between tasks. During walking, rearfoot eversion/inversion and external/internal rotation were strongly correlated with hip adduction/abduction (R = 0.69 and R = 0.84), whereas correlations with knee kinematics were not strong (R ≤ 0.51) and varied between subjects. The correlations with hip adduction/abduction were stronger than those with knee kinematics (P < 0.001). Most coefficients during single-leg landing were strong (R ≥ 0.70), and greater than those during walking (P < 0.001). Coupling angles indicated that hip motion relative to rearfoot motion was greater than knee motion relative to rearfoot motion during both tasks (P < 0.001). Interventions to control rearfoot kinematics may affect hip kinematics during dynamic tasks. The coupling motion between the rearfoot and hip/knee joints, especially in the knee, should be considered individually.