Knee OA Pain: Wedge Insoles Show Little Benefit
A meta-analysis of pooled data from 12 studies of lateral wedge insoles in the treatment of medial knee osteoarthritis (OA) showed modest improvement associated with wedge insoles in the overall analysis but no significant or clinically important effect on OA pain when wedge insoles were compared with neutral insoles, according to a study published in the August 21 issue of JAMA. The authors conclude that wedge insoles are ineffective, but other experts suggest that the neutral insoles might have provided something other than a placebo effect, such as shock absorption.
Matthew J. Parkes, BSc, from the University of Manchester, England, and colleagues conducted a meta-analysis to assess the efficacy of lateral wedge treatments (shoes and insoles designed to reduce medial knee compartment loading) in reducing knee pain in patients with medial knee osteoarthritis. The analysis included randomized trials of shoe-based treatments (lateral heel wedge insoles or shoes with variable stiffness soles) to a neutral or no-wedge control condition. Wedges were at 5° to 15° of angulation, which reduces the external knee adduction moment (torque). The pooled data included 885 patients, of whom 502 had received lateral wedge treatment.
The overall effect estimate of the 12 trials taken together was that lateral wedge treatment was associated with a moderate reduction in pain (an effect of −2.12 points on the Western Ontario and McMaster Universities Arthritis Index [WOMAC] pain scale). However, the effects were highly heterogeneous across studies, small-study bias was a problem (small studies were more likely to have reported positive effects of wedge insoles than were larger studies), and outcomes were affected by whether the comparison group involved a neutral insole or nothing.
“[A]mong trials comparing wedge insoles with neutral insoles, there were no significant or clinically important effects of laterally wedged insoles on knee pain,” the authors note. The lateral wedges were associated with a decrease of −0.12 points on the WOMAC pain subscale, which is below the minimal clinically important difference.
“These results suggest that compared with control interventions, lateral wedges are not efficacious for the treatment of knee pain in persons with medial knee osteoarthritis,” the authors conclude.
“I think this is a well-executed meta-analysis of lateral wedge insoles. The authors’ choice was not to include studies that compared lateral wedged insoles to concomitant therapy without a control. However, they decided to include studies comparing lateral wedged insole to neutral soles, which in my opinion is also a concomitant therapy. Perhaps shock-absorbing (neutral) soles can contribute to reduction of knee pain. Figure 2 [in the article] shows forest plots in favor of lateral wedged insoles in all control groups and overall. You could also conclude that inlays have an effect on knee pain reduction (placebo or not). I think the conclusion that lateral wedged insoles are not efficacious compared with control intervention is out of place because neutral soles may also have a positive effect, and are thus not a control intervention,” Dr. van Raaij said.
Dr. Raaij suggested that there is still a place for lateral wedged insoles in the pain management of medial knee OA in women with less severe knee OA.
JAMA. 2013;310:722-730. Abstract
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