Knee hyperextension in chronic stroke: Associated biomechanical and neuromuscular factors

This study aimed to determine the gait phase in which knee hyperextension occurs in stroke patients and to investigate the factors associated with knee hyperextension.

This study included 30 stroke patients aged between 40 and 70 years with maximum knee hyperextension during the stance phase of gait. Muscle strength was evaluated with manual muscle test, and muscle tone was assessed with the Modified Ashworth Scale. Kinematic evaluation of the patients was made using the motion analysis system. Additionally, categorisation was made according to the stance phase of gait, where knee hyperextension was at its highest.

A weak relationship was found between maximum knee hyperextension angle and gastrocnemius spasticity, a moderate relationship between knee flexor muscle strength, and a moderate relationship between ankle dorsiflexor muscle strength. In addition, a weak relationship was found between the maximum knee hyperextension and pelvic retraction angles. According to this clustering, it was observed that 66.67 % of the participants (20 people) showed maximum knee hyperextension in the single support phase. It was observed that the participants who had maximum knee hyperextension, especially after the mid-stance phase, had higher mean gastrocnemius spasticity. It was also observed that participants in Cluster 4, with a greater amount of maximum knee hyperextension, had the worst clinical parameters.

Our study observed that the degree of maximum knee hyperextension was related to knee flexor and ankle dorsiflexor muscle strengths, gastrocnemius spasticity and pelvic retraction. As clinical parameters worsened, maximum knee hyperextension was thought to occur late in the stance phase. Clinical Trial code:NCT05679700.