Altered biomechanical strategies of the paretic hip and knee joints during a step-up task: a pilot study

Abstract

BackgroundStroke often leads to chronic, neural-derived motor impairments in the paretic lower limb, such as weakness, abnormal extensor torque coupling, and reduced ranges of motion. These impairments can constrain lower extremity movement and negatively impact the ability to navigate uneven terrain. Quantification of biomechanical strategies used by individuals with chronic stroke to step up would offer insight into the neural consequences of a stroke.Research QuestionWhat are the altered kinetic and kinematic strategies of the leading paretic hip and knee joints while swinging and pulling-up onto a step?MethodsA total of 10 participants were included in this mixed design study: 5 adults with hemiparetic stroke and 5 age-matched adults without stroke. Participants were instructed to step up onto a 4-inch platform, where joint kinetic and kinematics of the hip in the frontal plane and the hip and knee in the sagittal plane were quantified. A mixed effects linear regression model with two fixed effects of group (stroke and control) and lower limb (LL: dominant/non-paretic and non-dominant/paretic) was used to compare peak joint torques and angles. Another mixed effects model with two fixed effects of peak hip and knee extension torque was used to investigate whether these main effects could predict peak hip abduction torque.ResultsAltered biomechanical strategies of the paretic limb for step ascent included reduced sagittal plane flexion angles during swing, reduced hip abduction and knee extension torque combined with increased hip extension torque during pull-up stance, and abnormal torque coupling between the hip adductors and sagittal plane extensors.SignificanceThese differences can be linked to the neural consequences of a hemiparetic stroke, including corticospinal damage and upregulation of bulbospinal pathways as compensation. Overall, our findings can inform interventions for individuals with chronic stroke in navigating uneven terrain to maximize daily community activity.