Influence of knee hyperextension persisting into preswing on swing-phase kinematics through forward propulsion in poststroke hemiparetic gait

BACKGROUND: Poststroke hemiparetic gait often involves stance-phase knee hyperextension (genu recurvatum). Knee hyperextension persisting into preswing (PSw) can influence push-off and the subsequent swing-phase kinematics. This study investigated whether PSw hyperextension was associated with reduced forward propulsion and altered swing-phase kinematics, including functional limb shortening and peak knee-flexion angle. METHODS: Thirty patients with chronic poststroke hemiparesis and knee hyperextension were evaluated. Three-dimensional motion capture and force plates were used to measure overground walking. The outcome measures were peak forward propulsive force and swing-phase kinematics, specifically peak knee-flexion angle and functional limb shortening (quantified by the minimum pelvistoe distance). Patients were classified according to the presence of PSw hyperextension. Group differences and relationships among variables were examined using t-tests and correlation analyses. Path analysis assessed whether the relationship between PSw hyperextension and swing-phase kinematics was partly mediated by forward propulsion. RESULTS: Patients with PSw hyperextension showed significantly reduced forward propulsion and impaired functional limb shortening compared with those with knee hyperextension limited to earlier stance phases. Path analysis suggested that PSw hyperextension was associated with impaired functional limb shortening during swing, partly through reduced forward propulsion and partly through mechanisms independent of forward propulsion. SIGNIFICANCE: PSw hyperextension was associated with reduced forward propulsion and impaired functional limb shortening in patients with hemiparetic stroke. Addressing PSw hyperextension may help improve swing-phase mechanics during gait rehabilitation.