Increased ankle pushoff alters frontal-plane hip and knee mechanics

In a simple model of bipedal walking, both a muscle moment at the hip and an impulsive push generated through ankle plantarflexion power gait. There is a biomechanical tradeoff between ankle and hip moments in the sagittal plane. Although ankle pushoff is primarily sagittal, its impact on frontal-plane mechanics, which are related to hip and knee injury risk, remains underexplored. This study aimed to investigate how increased ankle pushoff influences frontal-plane hip and knee moments during level walking. Understanding these effects could guide treatments for individuals with hip or knee symptoms linked to frontal-plane mechanics. Thirty-seven healthy adults walked on an instrumented treadmill under two conditions: Habitual (typical gait) and Push (increased ankle pushoff). Kinematic and kinetic data were collected and normalized for gait cycle and body weight. Statistical parametric mapping and peak value analysis were used to compare differences in internal joint moments and angles between conditions. Increased pushoff was confirmed by greater ankle plantarflexion moments and angular impulse in the Push condition. At the hip, increased pushoff resulted in a greater abduction moment early in stance and a reduced abduction moment and adduction angle late in stance. At the knee, increased pushoff led to a greater abduction moment late in stance. These findings suggest that increasing ankle pushoff during walking has significant effects on hip and knee frontal-plane biomechanics, which may not be beneficial for individuals with conditions influenced by hip and knee abduction moments.