Immediate effect of Masai Barefoot Technology shoes on knee joint moments in women with knee osteoarthritis

Highlights

• We evaluated the effect of MBT shoes on external knee moments in women with knee OA.

• The knee flexion moment was significantly reduced while walking with the MBT shoes.

• The knee adduction moment did not differ statistically between the MBT shoes and control shoes.

• MBT shoes did not increase compensatory lateral and anterior trunk lean while walking.

• MBT shoes may reduce knee loading without increasing compensatory trunk lean in women with knee OA.

Abstract

Footwear modification can beneficially alter knee loading in patients with knee osteoarthritis. This study evaluated the effect of Masai Barefoot Technology shoes on reductions in external knee moments in patients with knee osteoarthritis. Three-dimensional motion analysis was used to examine the effect of Masai Barefoot Technology versus control shoes on the knee adduction and flexion moments in 17 women (mean age, 63.6 years) with radiographically confirmed knee osteoarthritis. The lateral and anterior trunk lean values, knee flexion and adduction angles, and ground reaction force were also evaluated. The influence of the original walking pattern on the changes in knee moments with Masai Barefoot Technology shoes was evaluated. The knee flexion moment in early stance was significantly reduced while walking with the Masai Barefoot Technology shoes (0.25 ± 0.14 N m/kg m) as compared with walking with control shoes (0.30 ± 0.19 N m/kg m); whereas the knee adduction moment showed no changes. Masai Barefoot Technology shoes did not increase compensatory lateral and anterior trunk lean. The degree of knee flexion moment in the original walking pattern with control shoes was correlated directly with its reduction when wearing Masai Barefoot Technology shoes by multiple linear regression analysis (adjusted R² = 0.44, P < 0.01). Masai Barefoot Technology shoes reduced the knee flexion moment during walking without increasing the compensatory trunk lean and may therefore reduce external knee loading in women with knee osteoarthritis.

Introduction

The rate of progression of osteoarthritis (OA) at the knee is associated with increased loads in the joint during ambulation [1]. Footwear modification for patients with knee OA has received attention as an effective conservative intervention that can alter knee load [2]. A series of related previous studies have shown that variable-stiffness shoes [3], mobility shoes [4], flat walking shoes [5], flexible non-heeled shoes [6], and shoes with lateral wedging and a variable-stiffness sole [7] can reduce knee joint loading while walking as compared to modern heeled shoes or stability shoes. These previous studies have focused on the changes in the external knee adduction moment (KAM), however, Walter et al. [8] confirmed that decreased KAM does not necessarily guarantee decreased medial compartment contact force of the knee during gait. In their report, regression analysis demonstrated that the peak value of medial contact force was best fitted by a combination of peak value of the KAM and external knee flexion moment (KFM). Therefore, an evaluation of gait modifications for reducing the medial contact force should consider both KAM and KFM. However, with the exception of a report by Bennell et al. [7], KAM and KFM while wearing modified shoes have not been simultaneously analyzed in patients with knee OA.

Thus far, increased lateral and anterior trunk lean is one of the most effective gait modifications for reducing knee loading during walking [9]. Increased lateral trunk lean toward the symptomatic knee and increased anterior trunk lean have been shown to reduce the KAM and KFM, respectively, in patients with knee OA and those who have undergone total knee arthroplasty [10], [11]. To determine the exact effects of shoe modifications on knee moments, it is necessary to examine changes in the trunk lean during walking. However, no studies have examined gait modifications along with the changes in trunk motion that accompany changes in shoe types.

Masai Barefoot Technology (MBT) shoes (Masai Marketing & Trading AG, Winterthur, Switzerland) are a type of shoes specialized in altering the biomechanics of the lower extremity during standing and walking. MBT shoes are characterized by a round sole in the anteroposterior direction and a flexible heel. By using MBT shoes, a decreased range of motion in the hip and the knee joints, which were assumed to be due to decreased walking speed and stride length, along with increased ankle dorsiflexion at initial contact have been reported [12]. Meanwhile, at the same walking speed, the kinematics and angular impulse for all lower extremity joints were noted to be similar in MBT and control shoe conditions, except for increased ankle dorsiflexion during the first half of stance [13]. Our previous study showed that ground reaction force decreased at the shock absorption and progression phases when wearing MBT shoes [14]. Moreover, for the knee joint, reduced peak KAM and KFM during early stance and increased peak KFM in late stance were observed when walking with MBT shoes in young and the elderly individuals [15]. Reduced peak KAM in early stance was also demonstrated in overweight individuals who were free from knee pain [16]. For both one-leg standing and walking, trunk lean in both the frontal and sagittal planes tended to increase with a foam support surface as compared to that with a normal floor [17]. Therefore, lateral and anteroposterior trunk lean should be measured when walking with MBT shoes, which have a flexible heel coupled with a round sole.

It is possible that MBT shoes may have a beneficial effect on knee loading for patients with knee OA. However, to date, the effects of MBT shoes on gait biomechanics in patients with knee OA have not been investigated. The purpose of the current study was therefore to evaluate the effect of MBT shoes on reductions in external knee moments in women with knee OA. We hypothesized that external knee moments during walking would be reduced in women with knee OA by wearing MBT shoes without increasing the lateral or anterior trunk lean adopted as gait compensation.