Determining the Delay Time of the Muscles Around the Knee Joint in Response to Rotational Perturbation From Support Surface

Introduction: Knee joint injuries usually occur in a short time, so analyzing the mechanism and process of this short time can be helpful to prevent similar injuries. This study aimed to determine and compare the reaction time of knee muscles and investigate the effect of knee position and perturbation direction on the reaction time of knee muscles in response to horizontal rotational perturbation applied to lower leg from support surface area. Materials and Methods: A total of 30 healthy women volunteers were received ±35 degrees of horizontal rotational perturbation and speed of 120 degrees per second from the sole while standing on the right leg in four conditions (external versus internal rotation of surface while the knee was in both extension and flexion position). Electromyography of knee muscles (vastus medialis and lateralis, medial and lateral hamstring and medial and lateral gastrocnemius) was measured to study the reaction time. Results: The reaction time of knee muscles during the perturbation was relatively long in this study (124 to 151 ms). It seems that muscles are recruited simultaneously in most conditions except in external rotation perturbation, with extension knee that the internal gastrocnemius muscle had significantly less delay time than the internal hamstring (P<0.05) and external quadriceps (P<0.05). The results show that most of these muscles do not react selectively and dependently on perturbation direction and knee position in response to horizontal rotational perturbation. Conclusion: In this study, little difference was seen in the reaction time of most knee muscles in all conditions. Thus in response to this type of perturbation, the knee muscles showed co-contraction.