Lateral wedge insoles are ineffective, compared with control interventions, for reducing pain in patients with medial knee osteoarthritis, according to a meta-analysis of data from 12 randomized, controlled trials.
The findings of this meta-analysis suggest that although lateral wedge insoles have been considered a possible means for reducing medial loading by easing "the physical stress applied to that compartment of the joint" and thereby reducing painful knee symptoms, the available evidence does not support their use for this indication, first author Matthew J. Parkes of the University of Manchester (England) Institute of Inflammation and Repair and his colleagues reported. The study was published in the Aug. 21 issue of JAMA.
"...We found that compared with neutral inserts, lateral wedges had no association with knee pain (SMD, -0.03) and heterogeneity was much lower across trial findings."
When data from all 12 trials were considered, the overall effect estimate for lateral wedge insoles was a standardized mean difference (SMD) in pain between interventions of –0.47. This represents moderately significant pain reduction for lateral wedges, and translates into an effect size of –2.12 on the 0-20 Western Ontario and McMaster Universities Arthritis Index (WOMAC) pain scale.
However, the effects were highly heterogenous across the studies, and a significant difference in treatment effect was noted based on the type of control condition used, with a lesser effect seen in the seven trials that used a neutral wedge as the control, the investigators said.
"When trials were grouped according to the control group treatment, we found that compared with neutral inserts, lateral wedges had no association with knee pain (SMD, -0.03) and heterogeneity was much lower across trial findings," they wrote.
The SMD of –0.03 based on these studies represented an effect size of only –0.12 between lateral wedges and neutral wedges on the WOMAC pain subscale (JAMA 2013;310:722-30).
The investigators identified the studies included in the meta-analysis through an extensive search of the literature, including searches of multiple databases for studies published from the earliest available date to May 2013. The 12 trials that met inclusion criteria involved a total of 885 patients, including 502 who received lateral wedge treatment. The primary outcome in the trials was self-reported pain.
The findings are of note because the results of studies examining knee pain following treatment have been inconsistent, and have led to conflicting recommendations.
"For example, in recent osteoarthritis treatment guidelines, the American College of Rheumatology did not recommend lateral wedge insoles as a treatment for medial knee osteoarthritis. On the other hand, the Osteoarthritis Research Society International treatment guidelines state, ‘Lateral wedged insoles can be of symptomatic benefit for some patients with medial tibiofemoral compartment [osteoarthritis] OA,’ " the investigators wrote, adding that in the United Kingdom, the National Institute for Health and Care Excellence considers "footwear with shock-absorbing properties" to be worth consideration in the absence of well-designed trial data.
The identification of effective nonsurgical treatment for knee OA is a high priority, given the increasing prevalence of the disease, the limited efficacious treatment options, and the increase in the rates of knee replacement, they said, noting that medial osteoarthritis is one of the most common subtypes of knee osteoarthritis.
This study was funded by a grant from Arthritis Research UK and by a grant from the National Institute for Health and Care Excellence to two individual authors. Multiple authors disclosed potential conflicts of interest, including a National Institute for Health Research clinical doctoral fellowship; institutional salary or grant support from Arthritis Research UK, serving as a consultant for Sunovion Pharmaceuticals and Knee Creations Ltd., and as associate editor for Arthritis Care & Research; serving as a continuing medical education activity editor and receiving payment for CME case presentations from Vindico Medical Education; and receiving grants from the Arthritis Foundation, the National Institute on Aging, and the Foundation for Physical Medicine & Rehabilitation.