Categorizing knee hyperextension patterns in hemiparetic gait and examining associated impairments in patients with chronic stroke

Background: Post-stroke hemiparetic gait exhibits considerable variations in motion patterns and abnormal muscle activities, notably knee hyperextension during the stance phase. Existing studies have primarily concentrated on its joint angle or moment. However, the underlying causes remain unclear. Thus, the causes of knee hyperextension were explored from a new perspective based on temporal-durational factors. Research Question: Does the temporal-durational difference of knee hyperextension presence result from specific decreased motor functions? Methods: Barefoot gait at a comfortable speed was captured using a three-dimensional camera system. Scores of knee hyperextension used a metric with the temporal-durational factor of knee hyperextension presence in each of four stance phases (1st double support, DS1; early single-leg stance, ESS; late single-leg stance, LSS; 2nd double support, DS2). These scores were used in cluster analysis. The classification and regression tree analysis characterizing each knee hyperextension cluster used the clinical measures of the lower limb and trunk motor function, muscle strength, and spasticity as explanatory variables. Results: Thirty patients with hemiparetic chronic stroke who exhibited knee hyperextension during gait were included. Four knee hyperextension clusters were shown: Momentary (almost no hyperextension), Continuous (DS1-DS2), ESS-LSS, and ESS-DS2. Knee flexor strength was lower in the groups with long hyperextension durations (Continuous and ESS-DS2) compared with short durations (ESS-LSS and Momentary). ESS-DS2 exhibited higher trunk motor function than Continuous, whereas more severe spasticity was observed in ESS-LSS than in Momentary. Significance: This study successfully classified four hemiparetic gait patterns with knee hyperextension based on the temporal-durational factor, providing valuable perspectives for understanding and addressing specific functional physical impairments. These findings offer guidance for focusing on related physical functions when striving for gait improvement with knee hyperextension and are expected to serve as a reference for treatment decision-making.