The Effect of Lateral Wedge Insole on Coordination and Coordination Variability in young Individuals with Varus Knee during Walking

Varus knee is one of the most common malalignments that alters force absorbing in cross the knee[1]. Any change in the tibiofemoral angle could affect the compartment force distribution in genu varum associated with joint malalignment. In varus knee, more than an assumed issue, the load is predominantly in medial compartment[2]. During simulating one-legged weight bearing stance by moving the upper body gravity closer to the knee joint, 75 percent of the joint load passed through the medial knee compartment[1]. On the other hand, Standing posture of Anatomical alignment or with a greater knee abduction a higher risk was observed for injury during dynamic activity[3]. Brouwer [4] in a follow-up study in 2007 examined 1501 participants and reported 62 percent with osteoarthrosis associated with varus and valgus knee. In addition, by examining varus alignment in osteoarthritis patients, this malalignment was found to be associated with a greater risk of medial osteoarthritis progression[5]. Many studies [6, 7] examined LWI as a pathway for EKAM reduction, showing a offloading in medial knee compartment forces. Many studies were performed on pain reduction and OS progression prevention, including those working on patients with OS combine varus knee that suggested LWI for EKAM reduction. Along with these studies, there are some studies that used this orthosis on healthy subjects with varus knee with no significant OS, in order to decrease medial knee compartment mechanical load as a biomechanical risk factor [8, 9]. The treatment of knee OS Abaddon in limited ways such as using orthosis for pain reduction and prevention of knee OS progression. However, in the healthy subjects with knee varus, it is more important to be sure about the possible interruptions and effectible side-effects of using orthosis on gait pattern. It was assumed that the LWI with shifting COP under the feet has an special effect on joints[6]. In those studies conducted on healthy participants for the assessment of category, a few articles were found that examined LWI on gait kinematic. [7] as a result, they reported that LWI had no effect on lower extremity kinematics in gait for healthy participants and [10] also found a significant effect of LWI on gait kinematic. The analysis of subjects with joint kinematics alone cannot be adequate to recognize the coordination and neuromuscular control between multiple joints [11]. As well, Multi-joint coordination involves a complicated neuromuscular control to regulate locomotion integrating with proprioceptive sense, vestibular, and optical ones[12, 13]. On the other hand, immoderate coordination variability can imply an unstable motor control, and besides, inadequate variability may indicate a more rigid and constricted movement pattern[11]. Thereafter, it is important to understand how the body adjust its movement strategy to responding to the change with the use of each kind of interruptive factors like using orthosis [13, 14]. Vector codding and continues relative phase (CRP) are the two less used methods for measuring joint and segment coordination and coordination variability between two movements. Of note, against vector coding, CRP limits the analysis of coordination to the phase relationship. Vector codding and four coordination phases indicate the relationship between the two movements, including in-phase or anti-phase. Accordingly, this parameter is derived from the limb angles containing both spatial and temporal information related to one movement or segment over another one[15]. According to a previous studies [16, 17], wearing foot orthosis may realign the lower-extremity and may also affect joints coordination. In a recently published study, some researchers were working on arch support foot insole in subjects with foot flat to examine the effect of orthosis on both coordination and variability. According the previous hypothesis, footwear effects on gait have been mechanical such as changing stride length, cadence reduction, rise in single support time, and an increase in mass of the distal segment of the shoe during walking[16]. [18] They reported that using arch support can be effective on changing low limb coordination and coordination variability in walking (children). However, no significant effect was observed on the coordination pattern and coordination variability of shank-thigh and foot-shank during landing[19]. In addition, [20] different coordination patterns of bracing were found in individuals with and without chronic ankle instability, and ankle taping has been shown to change foot-shank coordination and reduce coordination variability during walking among both healthy and chronic ankle instability participants[21]. To the best of our knowledge, there is no study examining coordination and coordination variability of LWI during the gait in participants with coxa vara so for. In order to provide the additional information to the kinematics of movement, this investigation adapted LWI to aid clinicians and researchers to certain the knee dysfunction, like a knee instability, range of motion and proprioception, etc. Accordingly, this study aimed to examine the effect of LWI on lower-extremity coordination and coordination variability during gait in healthy individuals with varus knee. Analysis of the effect of LWI on lower-extremity coordination strategies could be considered as a start for systematic and potentially distinct movement adaptations that contributes into bracing efficacy in subjects with coxa vara. Correspondingly, this hypothesis states that there would be greater antiphase coordination.