Published: Aug 20, 2013
By Crystal Phend, Senior Staff Writer, MedPage Today

Full Story:  http://www.medpagetoday.com/Rheumatology/Arthritis/41099

Lateral wedge shoe insoles didn’t appear to ease medial osteoarthritis knee pain beyond a placebo effect, according to a meta-analysis.

The orthotics did have a significant impact compared with controls overall, the equivalent of 2.12 fewer points on the 20-point Western Ontario and McMaster Universities Arthritis Index (WOMAC) pain scale, Matthew J. Parkes, BSc, of England’s University of Manchester Institute of Inflammation and Repair, and colleagues found.

But that impact was largely in studies with a higher risk of bias from using regular shoes without inserts as a control, the group reported in the Aug. 21 issue of theJournal of the American Medical Association.

Trials that used a neutral, or flat, shoe insert for better blinding in the control group consistently showed no significant or clinically important impact from lateral wedges. The pooled effect was only the equivalent of 0.12 fewer points on the WOMAC scale versus controls.

“This suggests an anticipation bias on the part of subjects who expect a benefit with the intervention compared with no intervention,” commented Marc C. Hochberg, MD, MPH, head of rheumatology and clinical immunology at the University of Maryland in Baltimore.

“The clinical implications are for healthcare practitioners not to recommend lateral wedge insoles and for patients not to buy them,” he added in an email to MedPage Today.

The shoe inserts — custom or off-the-shelf — have been a popular remedy in medial osteoarthritis, but Eric Matteson, MD, chair of rheumatology at the Mayo Clinic in Rochester, Minn., also predicted a decline in use based on the results.

“The intervention is very easy to do and it has been thought that does help to reduce pain,” he said in an interview. But “the effect of the wedging just isn’t as good as what had been hoped.”

The idea has been that the angled wedge transfers some of the load on the knee away from the internal compartment of the joint in medial osteoarthritis.

The explanation for why it didn’t work in the meta-analysis may be that the 5% to 6% reductions in the “external adduction moment” (a measure of medial versus lateral loading) across the knee by inserts wasn’t enough to impact pain, but more angulation wasn’t any better in the one trial that tested it and is less tolerable, Parkes’s group noted.

Another possibility is that “pain, being a self-reported, subjective outcome, is particularly susceptible to [placebo] effects, and such influences have been documented in reviews of osteoarthritis literature,” they noted.

Still, Matteson suggested that there might be subtypes or subgroups in medial osteoarthritis that may benefit from lateral wedge insoles and would be worth further study in larger trials.

The meta-analysis included 12 randomized, controlled trials with a total of 885 participants who received lateral wedge treatment (insoles in all but one, which used shoes with variable stiffness sole) for medial knee osteoarthritis.

Despite the relatively small number of trials included, the researchers noted that the 95% confidence intervals were narrow enough to exclude a substantial clinical benefit from lateral wedge treatment compared with neutral inserts.

The upper bound was a 0.18 reduction in the standard mean difference, representing a 0.81-point reduction on the 20-point WOMAC pain scale.