Researchers from the UK have conducted a meta-analysis showing that wedge insoles may not go far in reducing knee pain. This work, published in the August 21, 2013 issue of the Journal of the American Medical Association found that among trials comparing wedge insoles with neutral insoles, there was no significant or clinically important association between use of wedge insoles and reduction in knee pain.
The study authors note: “The increase in rates of knee replacement for osteoarthritis [OA] has made the identification of effective nonsurgical treatments a high priority. Medial osteoarthritis is one of the most common subtypes of knee osteoarthritis. One type of treatment for medial knee osteoarthritis involves reducing medial (inner) loading to ease the physical stress applied to that compartment of the joint. The wedge is placed under the sole of the foot and angulated so that it is thicker over the lateral than the medial edge, transferring loading during weight bearing from the medial to the lateral knee compartment.”
Matthew J. Parkes, B.Sc., of the University of Manchester, England, and colleagues set out 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 authors conducted a search of the medical literature to identify randomized trials that compared shoe-based treatments (lateral heel wedge insoles or shoes with variable stiffness soles) aimed at reducing medial knee load, with a neutral or no wedge control condition. The wedge needed to be of 5° to 15° of angulation, which is a level shown in previous studies to reduce external knee adduction moment (torque). Studies must have included patient-reported pain as an outcome. Twelve trials met inclusion criteria with a total of 885 participants of whom 502 received lateral wedge treatment.
The researchers found, when considering all 12 trials, the overall effect estimate was a standard mean difference in pain between interventions that showed a moderately significant effect of a lateral wedge on pain reduction. However, the findings were highly heterogeneous across studies. Larger trials with a lower risk of bias suggested a null association.
When trials were grouped according to the control group treatment, the authors found that compared with neutral inserts, lateral wedges had no association with knee pain and heterogeneity was much lower across trial findings.
Matt Parkes told OTW, “The fact that the flat vs. wedged insole trials were so consistent in showing no superiority of wedges over flat insoles was perhaps unexpected, given the wide-ranging opinions both in support of and against wedges. So, aside from a placebo effect, wedge insoles provide little arthritis pain relief.”
Custom orthotic insoles I have personally found to help stabilize knee pain. But TKR for severe OA is the tx.
My first step post-op weight bearing on tkr felt like “the tire was no longer flat” my knee felt stable inside w/o pain from irregular bones rubbing. It was wonderful, the rest of the pain was tolerated knowing in 2-3 months I would be full function again.
This research article article and the photo included with the article is very short sighted and misleading.
One of the primary reasons for medial knee pathology is hyperpronation. Whether it is congenital, secondary to tibial position, due to an equinus deformity or a myriad of other reasons, over pronating is the root cause of medial knee pain much of the time. Adding a lateral wedge, depending on the foot type, will actually cause more calcaneal eversion leading to even more pronation, thereby worsening the problem.
The short sightedness comes, in my opinion, from not comparing functional orthotic devices to a simple insole with a rearfoot wedge (as noted in this article).
By controlling the rearfoot into a better functioning position you allow the whole foot to function better, allowing a stable and neutral platform from which to walk. Having said that the study may have been better served if it compared the old style custom rigid orthotic devices with the new cad cam, machine milled orthotic devices or the plain insole vs. a functional orthotic device and the effect on medial knee pathology.
Just the title of this article will leave many of our colleagues shaking their heads that they already knew insoles were a waste of time and money…