Changes in knee adduction moment, pain, and functionality with a variable‐stiffness walking shoe after 6 months

Abstract

This study tested the effects of variable-stiffness shoes on knee adduction moment, pain, and function in subjects with symptoms of medial compartment knee osteoarthritis over 6 months. Patients were randomly and blindly assigned to a variable-stiffness intervention or constant-stiffness control shoe. The Western Ontario and McMaster Universities (WOMAC) score served as the primary outcome measure. Joint loading, the secondary outcome measure, was assessed using the external knee adduction moment. Peak external knee adduction moment, total WOMAC, and WOMAC pain scores were assessed at baseline and after 6 months. The total WOMAC and WOMAC pain scores for the intervention group were reduced from baseline to 6 months (p ¼ 0.017 and p ¼ 0.002, respectively), with no significant reductions for the control group. There was no difference between groups in magnitude of the reduction in total WOMAC (p ¼ 0.50) or WOMAC pain scores (p ¼ 0.31). The proportion of patients achieving a clinically important improvement in pain was greater in the intervention group than in the control group (p ¼ 0.012). The variable-stiffness shoes reduced the peak knee adduction moment (À6.6% vs. control, p < 0.001) in the 34 intervention subjects at 6 months. The adduction moment reduction significantly improved (p ¼ 0.03) from the baseline reduction. The constant-stiffness control shoe increased the peak knee adduction moment (þ6.3% vs. personal, p ¼ 0.004) in the 26 control subjects at 6 months. The results of this study showed that wearing the variable-stiffness shoe lowered the adduction moment, reduced pain, and improved functionality after 6 months of wear. The lower adduction moment associated with wearing this shoe may slow the rate of progression of osteoarthritis after long-term use. ß

Effect of center of pressure modulation on knee adduction moment in medial compartment knee osteoarthritis

“…Previous studies confirmed the effectiveness of unloading the diseased articular surface in knee OA patients. [28][29][30][31] Our results verify that KAM can be effectively influenced by foot-generated COP manipulations in various stages of the disease.…”

Kinematic adaptations to a variable stiffness shoe: Mechanisms for reducing joint loading

“…A comparison of the dynamic changes associated with the variable stiffness shoe to kinematic changes in fixed interventions such as lateral wedge shoes might help to explain the difference in the clinical outcome (Erhart et al, 2010) with this shoe relative to the inconsistent results seen with wedged interventions (Kakihana et al, 2007;Toda and Tsukimura, 2004). The primary difference between response to lateral wedge interventions and the variable stiffness shoe is the direction of shift in the COP in combination with the change in the m-l GRF (Fantini Pagani et al, 2011;Kakihana et al, 2007).…”

“…A recent prospective randomized placebo controlled clinical trial found that pain was decrease by a clinically significant amount for patients wearing a variable stiffness shoe (Erhart et al, 2008;Erhart et al, 2010). This clinical benefit was attributed to the decrease in the external knee adduction moment, a change that has also been shown for a group of healthy subjects in this same shoe (Fisher et al, 2007).…”

A Biomechanical Perspective on Physical Therapy Management of Knee Osteoarthritis

“…Variable-stiffness shoes have been shown to significantly reduce the first peak in KAM by as much as 13% compared to constant-stiffness control shoes (TABLE 3). [41][42][43][44]99 Given that the magnitude of the GRF remains relatively unchanged when wearing variable-stiffness shoes, it has been suggested that reductions in KAM are related to a lateral shift in the center of pressure at the foot, which reduces the external KAM lever arm. 99 An instrumented knee replacement prosthesis that directly measured knee loading in a single patient found reductions of 13% in the first peak in KAM, 22% in the second peak in KAM, and 12% in the medial compartment joint contact force when walking with variable-stiffness shoes compared to personal shoes.…”

“…41 Clinical evidence also supports the effectiveness of variable-stiffness shoes in reducing knee pain and improving function after 6 and 12 months of continuous use. 42,44 Therefore, the use of variable-stiffness shoes seems to be an effective treatment strategy for reducing symptoms and medial compartment loading for patients with knee OA during gait.…”