Rear foot kinematics when wearing lateral wedge insoles and foot alignment influence the effect of knee adduction moment for medial knee osteoarthritis

Abstract

Lateral wedge insoles (LWIs) are prescribed for patients with medial knee osteoarthritis to reduce the external knee adduction moment (KAM). However, the biomechanical effects of LWIs are limited in some patients. The purpose of this study was to investigate whether the biomechanical effects of LWIs depend on individual foot alignment and to examine the relationship between change in KAM and changes in foot and ankle biomechanics when wearing LWIs. Twenty-one patients participated in this study. They were categorized into normal or abnormal foot groups based on the foot posture index (FPI). All patients were requested to perform a normal gait under barefoot and LWI conditions. A three-dimensional motion analysis system was used to record 1st and 2nd KAM, knee adduction angular impulse (KAAI), center of pressure displacement, and knee-ground reaction force lever arm. Furthermore, the foot and ankle frontal plane kinematic parameters were evaluated. The 1st KAM was significantly reduced under the LWI condition compared to that under the barefoot condition in the normal foot group. In contrast, there was no significant difference in 1st KAM between both conditions in the abnormal foot group. Decreased rear foot eversion strongly correlated with reduction in the 1st KAM in the normal foot group. These findings suggested that it is helpful to assess individual foot alignment to ensure adequate insole treatment for patients with medial knee osteoarthritis and that decreased rear foot eversion during the early stance phase is significantly involved in the reduction of 1st KAM when wearing LWIs with normal feet.

Comparison of the Asymmetries in Foot Posture and Properties of Gastrocnemius Muscle and Achilles Tendon Between Patients With Unilateral and Bilateral Knee Osteoarthritis

“…Furthermore, given that inter-limbs foot posture and tension of AT were more asymmetrical in unilateral KOA patients, and there was a positive association between asymmetrical FPI score and K/L grade, improving their asymmetries seemed to be critical. Insole could immediately correct foot posture, which should be a promising tool to modulate knee adduction moment for medial KOA ( Sawada et al, 2017 ). However, because less asymmetrical foot posture and properties were detected between two limbs, improving properties of AT and LG, such as decreasing their tone and stiffness, should be high on the list of priorities when treating bilateral KOA patients.…”

Frontal plane knee alignment mediates the effect of frontal plane rearfoot motion on knee joint load distribution during walking in people with medial knee osteoarthritis

“…In contrast, Sawada et al reported the opposite finding; that is, decreased rearfoot eversion was correlated with KAM reductions in people with neutral foot postures, determined statically when wearing LWIs 14 . Clarifying these important relationships are required to better guide KOA treatment approaches that rely on modification of foot posture or position, such as LWIs, to reduce KAM magnitudes, knee pain, and potential risk of OA progression.…”

“…Buldt et al 26 reported no statistically significant J o u r n a l P r e -p r o o f differences in KAM magnitudes among groups of individuals similarly categorized by the Foot Posture Index 27 , and also reported no correlation (r = 0.04) between rearfoot eversion and the early stance KAM peak. Using LWIs as a model, Sawada et al reported different changes in the KAM based on foot posture in both healthy individuals 28 and those with knee OA 14 . Finally, Koshino et al 29 reported that rearfoot kinematics in healthy individuals may be more closely coupled to hip kinematics than knee kinematics during walking.…”

An exploration of changes in plantar pressure distributions during walking with standalone and supported lateral wedge insole designs

“…Evaluations of pressure distribution underfoot with LWI have primarily reported lateral shifts in the centre of pressure (CoP) [ 9 , 14 , 15 ]. Lateralization of CoP is hypothesized to reduce the KAM by shifting the medially-oriented ground reaction force to shorten the frontal plane moment arm between the reaction force vector and the knee joint.…”