Identification of stiff-knee gait in stroke survivors.

Background: Stiff-knee gait is a common movement disorder in individuals with stroke; however, standardized criteria for its identification remain lacking. This study aimed to examine suitable criteria for identifying stiff-knee stroke survivors to facilitate comparisons across studies. Twenty-four stroke survivors (45.2±13.7 years old) and 24 age- and sex-matched controls (45.5±13.5 years old) with no known gait impairment participated in this study. Participants walked along a 10-m walkway at a self-selected comfortable speed. A motion capture system recorded the trajectories of retroreflective markers placed on specific body landmarks. The following knee flexion parameters during gait cycle were analyzed: (1) peak knee flexion during the swing period, (2) total range of motion (RoM cycle), calculated as the difference between maximum and minimum knee excursion during gait cycle, (3) RoM from toe-off to peak knee flexion ("RoM swing"), and (4) timing of peak flexion. Comparisons were made among control, paretic, and non-paretic limbs.

Results: Among the 21 stroke survivors identified with stiff-knee gait, the paretic limb showed reduced peak swing, RoM swing, and RoM cycle compared to both the control and non-paretic limbs, as well as earlier timing compared to the non-paretic limb only.

Conclusions: Among the four examined criteria to identify stiff-knee gait in stroke survivors, the most suitable are peak knee flexion during the swing period of less than 40°, and knee range of motion from toe-off to peak knee flexion of less than 12°.