Biomechanical implications of the negative heel rocker sole shoe: gait kinematics and kinetics

Rocker sole shoes are commonly prescribed to diabetic patients with insensate feet. Recent passage of the therapeutic shoe bill has drawn an increased focus to prescription rehabilitative footwear. The purpose of this work is to investigate the dynamics of lower extremity joints (hip, knee and ankle) with the application of a negative heel rocker sole shoe under controlled lab conditions. Forty normal adults volunteered for gait evaluations using controlled baseline and prescription negative heel rocker sole shoes. Three-dimensional motion analysis techniques were used to acquire kinematic and kinetic data using a six-camera Vicon 370 motion system and two AMTI force plates. No significant change in walking speed or stride length was seen with the negative heel rocker shoe, although cadence was increased. The most significant kinematic changes with the application of the negative heel shoe occurred at the ankle in the sagittal plane with increased plantarflexion at terminal stance. Significant hip and knee changes were also noted with increased mid-stance hip extension and knee flexion. The most significant kinetic effects were seen in the transverse plane followed by changes in the sagittal and coronal planes. Changes in power were mostly noted in the sagittal plane. Other statistically significant changes in gait kinematics and kinetics were observed, although the magnitudes and durations were limited and as a result were not considered clinically significant. The study results indicated the negative heel rocker shoe significantly altered proximal joint metrics (hip and knee). The most significant distal joint alterations were seen in sagittal plane ankle kinetics. These kinematic and kinetic changes, along with previously studied effects of pressure relief at the metatarsal heads, should aid medical professionals in prescribing prophylactic footwear.