Gait initiation and lateral wedge insole for individuals with early knee osteoarthritis

Highlights

• Early knee osteoarthritis is associated with longer gait initiation cycle.

• Anticipatory postural adjustment phase is longer in early knee osteoarthritis.

• Bipedal standing phase is longer in early knee osteoarthritis.

• Lateral wedge insole can improve locomotor phase in knee osteoarthritis.

Abstract

Background

People with knee osteoarthritis are at higher risk of postural deficits and locomotor adaptations which could be manifested in transient tasks like gait initiation. To better understand the effect of early knee osteoarthritis on gait initiation, we measured the gait initiation in two groups of early knee osteoarthritis and healthy age-matched controls and assessed the effect of lateral wedge insole in knee osteoarthritis group.

Methods

Twenty-one individuals with early knee osteoarthritis, mean (SD) age = 53.1 (7.4, years), and 19 age- and sex-matched asymptomatic healthy individuals, mean (SD) age = 47.5 (11.2, years), participated. Centre of pressure trajectories were used to quantify the two phases of gait initiation in barefoot condition: anticipatory postural adjustment, and locomotor phase. The immediate and four-week effect of lateral wedge insole and shod condition were also compared for individuals in knee osteoarthritis group.

Findings

Longer duration of anticipatory postural adjustment phase (P = 0.046), locomotor phase (P = 0.049), and total duration of gait initiation (P = 0.035) with lower length and velocity of the center of pressure trajectories in anticipatory postural adjustment phase (P = 0.002, and 0.008, respectively) were observed in knee osteoarthritis group compared to controls. Lateral wedge insole could increase the length and velocity of the centre of pressure in locomotor phase compared to barefoot condition (P = 0.001, and 0.002, respectively).

Interpretation

Our study outlined that people with early knee osteoarthritis adopt different gait initiation strategies mainly in postural preparation phase. The potential effect of lateral wedge insole was shown with better performance of the locomotor phase.

Clinical trial registry number

IRCT2016060628310N1.

Introduction

Osteoarthritis (OA) is one of the most common joint disorders that affects 19% to 43% of adults older than 40 years (Culvenor et al., 2018). Walking difficulty associated with knee OA combined with comorbidities of ageing, e.g., cardiovascular (Veronese et al., 2018), can contribute to risks of sedentary behaviors and decrease physical activities (Jayabalan et al., 2019), falls (Anderson et al., 2019), early mortality and hospitalization (Kendzerska et al., 2017).

Different studies reported locomotor and neuromuscular adaptations through trend of knee OA disease from incidence, i.e., determined with Kellgren & Lawrence radiographic classification (K&L) < 2 (Felson et al., 2011), to progression to late stage (Iijima et al., 2019; Mills et al., 2013). The knee adduction moment, as an indication of the compressive load at the medial tibiofemoral compartment, is the most commonly reported parameter in knee OA literature (Foroughi et al., 2009), and is associated with an increase in knee OA severity (Mündermann et al., 2005). However, there is no difference in knee adduction moment in gait of people with early knee OA (Duffell et al., 2014). But reduced postural stability and altered muscle activation patterns with an increase in gluteus medius, quadriceps and hamstrings activities have been reported (Duffell et al., 2014). Regardless of growing knowledge about gait in knee OA and the mostly conservative treatments aimed to improve the gait adaptations and decrease the knee adduction moment, little is known about gait initiation in individuals with knee OA.

The importance of gait initiation is that in spite of steady-state gait (Duffell et al., 2014; Mills et al., 2013; Mündermann et al., 2005), in which walking happens at a constant mean velocity (Najafi et al., 2010), gait initiation focuses on lower limbs distinctly as well as the couple of posture and locomotion. Gait initiation is a highly coordinated task which is divided into three phases (Fig. 1); The first phase is a destabilizing postural equilibrium from a standing bipedal posture to propel the centre of gravity (CoG) forward (Brunt et al., 1999). This phase is called “anticipatory postural adjustment” (APA) which occurred prior to gross movement of limbs. The APA starts with the backward and lateral displacement of centre of pressure (CoP) toward the heel of the swing limb, i.e., the limb initiates the gait, and prepares for weight transfer from bipedal posture to monopedal standing phase (Davidson and Wolpert, 2005). This motor sequence of CoP movements continues with the lateral movement toward the heel of the stance limb. The APA generates the forces and moments essential to propel the CoG forward and toward the stance limb. APA is followed by an execution phase which is called “locomotor phase” (LOC) (Brunt et al., 1999). The LOC involves monopedal (MP) phase, and bipedal (BP) standing phase (Davidson and Wolpert, 2005). MP phase starts with the forward displacement of CoP, which is at instant of transition to single-limb stance, and ends with heel-off of the stance limb or heel strike of the swing limb. In BP standing phase, the forward shift of CoP continues until the toe-off of the stance limb occurs (Davidson and Wolpert, 2005); See Fig. 1.

To date, most studies have focused on established knee OA (K&L ≥ 2) (Felson et al., 2011;Viton et al., 1999, 2000), because postural deficits and locomotor impairments are much more evident in people with severe knee OA than early knee OA (K&L < 2) (Viton et al., 1999, 2000). The neurophysiological studies have shown that control of gait initiation is a challenging task for every system, even healthy individuals (Deliagina et al., 2008). Also, longer gait initiation is associated with less stable movements in older adults and should be investigated in implementation of interventions for falls prevention (van Andel et al., 2019). Moreover, the gait initiation is a countless task in performing the activities of daily living. Therefore, it is important to improve the gait initiation in individuals with knee OA.

One possible strategy to improve the gait initiation is the use of foot insoles. Lateral wedge insoles are one of the most conservative treatment for knee OA that can improve pain (Felson et al., 2018), static postural balance in mediolateral direction (Zangi et al., 2018), and reduce risk of falls (Esfandiari et al., 2018). It has also been shown that foot insoles can shorten the gait initiation in healthy individuals and help them to reach the steady-state gait quicker in conjunction with improvement of dynamic postural balance in the mediolateral direction (Najafi et al., 2010).

The impairment of posture and locomotion in gait of individuals with knee OA may be related to the biomechanical limitations and adaptive changes in neural control (Mille et al., 2012), and could be evaluated by gait initiation as a functional activity (Brunt et al., 1999). Therefore, we aimed to measure the gait initiation parameters in individuals with early knee OA and compare them to age- and sex- matched asymptomatic healthy individuals. We hypothesized that individuals with early knee OA adapted different gait initiation compared to healthy individuals. The second aim of our study was to assess the immediate and four-week effect of lateral wedge insole on gait initiation of individuals with early knee OA.