Muscular coordination of knee motion during the terminal-swing phase of normal gait

Abstract

Children with cerebral palsy often walk with diminished knee extension during the terminal swing phase, resulting in a troublesome "crouched" posture at initial contact and a shortened stride. Treatment of this gait abnormality is challenging because the factors that extend the knee during normal walking are not well understood, and because the potential of individual muscles to limit terminal-swing knee extension is unknown. This study analyzed a series of three-dimensional, muscle-driven dynamic simulations to quantify the angular accelerations of the knee induced by muscles and other factors during swing. Simulations were generated that reproduced the measured gait dynamics and muscle excitation patterns of six typically-developing children walking at self-10 selected speeds. The knee was accelerated toward extension in the simulations by velocity-related forces (i.e., Coriolis and centrifugal forces) and by a number of muscles, notably the vasti in mid-12 swing (passive), the hip extensors in terminal swing, and the stance-limb hip abductors, which accelerated the pelvis upward. Knee extension was slowed in terminal swing by the stance-limb hip flexors, which accelerated the pelvis backward. The hamstrings decelerated the forward motion of the swing-limb shank, but did not contribute substantially to angular motions of the knee. Based on these data, we hypothesize that the diminished knee extension in terminal swing exhibited by children with cerebral palsy may, in part, be caused by weak hip extensors or by impaired hip muscles on the stance limb that result in abnormal accelerations of the pelvis.

Electrical Stimulation of the Rectus Femoris During Pre-swing Diminishes Hip and Knee Flexion During the Swing Phase of Normal Gait

“…This was done by increasing the excitation level of the RF by magnitudes ranging from 0.01 to 0.1 units (1 corresponds to maximum excitation drive) for a 100 ms period. Changes in the interactions between the stance-limb foot and the ground were characterized by a set of rotational and translational spring-damper units [36]. Hence, the ground reaction forces and moments were allowed to change in response to the perturbations in force, and the effects of these changes were implicitly included in the actions attributed to the muscle.…”

Adapting to change : influence if a microprocessor-controlled prosthetic knee on gait adaptations

“…We chose to look into this variable, because research in typically developing children the upward movement of the pelvis and velocity-related forces are the main contributors to the knee extension movement during swing. 140 However, we do not know if and how these findings are applicable on individuals with an amputation. This means that these results are exploratory of nature and should be interpreted with caution.…”

“…The mechanism by which the prosthetic knee is extended during swing is not well studied, but in children without an amputation velocity-related forces and muscle activity of predominantly the stance leg have been described. 140 During early and mid-stance, the hip abductors and extensors of the stance leg move the pelvis center of mass upwards. 140 This movement creates an external knee extension moment.…”

“…140 During early and mid-stance, the hip abductors and extensors of the stance leg move the pelvis center of mass upwards. 140 This movement creates an external knee extension moment. 140 During slow walking stance limb muscle activity has shown to be the main contributor to knee extension during swing, while at faster walking the velocity-related forces are dominant.…”

“…140 This movement creates an external knee extension moment. 140 During slow walking stance limb muscle activity has shown to be the main contributor to knee extension during swing, while at faster walking the velocity-related forces are dominant. 141 Whether these mechanisms are seen in individuals with an amputation and whether they are influenced by a user-adaptive prosthetic knee is unknown.…”