Two separate studies directly compared valgus knee bracing and wedged foot orthoses for reducing knee adduction moment in patients with osteoarthritis, but came to opposite conclusions. A third study suggests combining the two interventions may be the best solution.

By Barbara Boughton

Conservative biomechanical strategies for knee osteoarthritis (OA) have long included knee braces and foot orthoses. In the past 10 years, an increasing number of studies have analyzed the extent to which these devices decrease the external knee adduction moment (KAM), a surrogate marker for compressive forces acting on the knee.

Many patients prefer orthotics to knee braces, since the in-shoe devices are less cumbersome. But the question of whether knee braces or wedged orthoses are more effective in changing the biomechanical forces on the knee has remained unresolved.

This year, for the first time, two separate biomechanical studies compared the treatment modalities head-to-head. However, their findings did not resolve the lingering questions surrounding braces and wedged foot orthoses for knee OA. The two research groups, in fact, reached opposite conclusions: A research group from German Sport University in Cologne found that knee braces were more effective for reducing KAM, while a group from the University of Salford in Manchester, UK, found that wedged foot orthoses were superior.

It’s likely that these two studies will not be the last word on the subject of the efficacy of knee braces and wedge orthoses, but their different conclusions do point out the difficulties of this type of biomechanical research.

“You have to be careful in comparing different studies on knee braces and wedge orthoses when the populations are different, the interventions are different, and the biomechanical calculations are different,” said Richard Jones, PhD, senior lecturer in clinical biomechanics at the University of Salford. “The challenge is that the biomechanical results in different patients can be quite variable, and you have to follow up with patients in these studies to assess the true clinical effects.”

In addition, patients often are not adherent to either knee braces or foot orthoses, which can also make true clinical outcomes difficult to assess, he noted.

The contrasting conclusions about the efficacy of valgus knee braces versus wedge orthoses in the British and German studies may be related to differences in study design and brace type used by the different research groups, according to C.L. Hubley-Kozey, PhD, professor in the school of physiotherapy and school of biomedical engineering at Dalhousie University in Halifax, Nova Scotia, Canada.

Comparison studies

In the German study, a motion capture system and force platforms in a biomechanical laboratory were used to capture the knee adduction moment in 10 patients with medial knee OA while they wore a knee brace or a laterally wedged insole. The knee brace used was tested in two valgus adjustments (4° and 8°) and the insole was fabricated with an inclination of 4°. The research was published in the July 2012 issue of the Journal of Orthopaedic Research.¹

The researchers found that the second peak KAM decreased by 18% for the brace in 4° of valgus, 21% for the brace in 8° of valgus, and 7% for the wedged orthoses. Similarly, knee adduction angular impulse (KAAI) also decreased more with the brace than the wedged insole (14%, 18%, and 7%). Whereas KAM reflects a single point in time during stance, KAAI is a measure of KAM as a function of time. Increased stance time in individuals with knee OA is thought to be related to painful symptoms.² Knee angle in the frontal plane during gait also reached a more valgus position with the knee brace, the researchers reported.

“The brace used in this study was a pretty cumbersome and heavy brace with straps close to the ankle and hip,” commented Hubley-Kozey, who suggested that although the brace in the study might have been more effective than the wedge orthoses, its design was one that patients might find uncomfortable and difficult to wear.

The British study³ used a lighter off-the-shelf knee brace and custom wedged foot orthoses designed with an arch support to increase patient comfort. The knee brace was set at 4° of valgus alignment and the wedged insole was inclined at 5° at the heel.

Twenty eight patients with medial tibiofemoral OA were analyzed before and after wearing each device for two weeks, with a two-week washout period between interventions. The testing involved a minimum of five walking trials at a self-selected pace in the biomechanics laboratory.

The British researchers found that both the knee brace and lateral wedge orthoses significantly reduced the early stance external KAM but there was a significantly greater reduction with the wedged insole than the knee brace (12% vs 7%).  Likewise, the KAAI was significantly reduced with both intervention but the insole was associated with a significantly greater reduction than the brace (16.1% vs 8.6%). The findings were e-published by Gait & Posture in August.³

“A key differentiator between the lateral wedged insole we used and current prescriptive devices is that we combined the insole with an arch support. According to previous research done by our group and others, traditional wedge insoles can cause pain and discomfort –especially in the ankle,” said author Richard Jones of the University of Salford.

The study found no significant differences between the interventions in terms of pain, function, or stiffness. Jones noted that his group is planning future research on the insole used in the study to examine how much it might reduce discomfort and pain compared to more traditional wedged devices.

Although the patients in the study wore the brace for only a short time, the fact that measurements were not taken right away could account for the different findings in the British and German studies, Jones noted.

Comfort and compliance

The most difficult aspect of using knee braces and, to a lesser extent, wedged insoles, is that patients don’t adhere to their therapy because the braces or insoles can be uncomfortable, according to Jones. In the British study, 71% of patients found the wedge orthoses comfortable enough to wear for more than four hours per day, while 71% wore the knee brace for less than four hours a day—which could account for the greater efficacy seen with the wedge orthoses, Jones said.

“It’s significant that the patients adhered to wearing the lateral wedged insole more than to wearing the brace,” Jones said. “The major challenge in designing studies that look at knee braces and wedge insoles is that you need follow up to ensure that the braces and insoles are being worn.“

Although knee braces are more likely to be viewed as cumbersome by patients, compliance can also be an issue with wedge foot orthoses.

Wedged insoles, because they put pressure on one side of a patient’s foot, may create discomfort or even pain, noted David Cooper, MD, director of orthopedic surgery at the Knee Center in Wilkes-Barre, PA.

“However, wedges can work for some patients and they are effective because they reduce loading on the knee,” Cooper said.

The American Academy of Orthopaedic Surgeons (AAOS), however, does not recommend either knee braces or wedge orthoses in their guidelines for knee OA.⁴

“The problem is that the scientific evidence is not there in regards to proving the efficacy of braces or orthotics,” said John Richmond, MD, professor of orthopedics at Tufts University School of Medicine in Boston. Richmond was involved in the development of the current AAOS Clinical Practice Guideline for treatment of knee OA. “Many of the studies in the literature aren’t restrictive enough in who they recruit in order to test the benefits of knee braces or orthotics.”

In Richmond’s clinical experience, knee braces often don’t work for overweight patients, because the brace has to be uncomfortably tight to reduce pressure on the surface on the knee.

“So the brace becomes as uncomfortable as the osteoarthritis pain,” Richmond said.

Richmond noted that he does use knee braces and orthoses for his patients with knee OA who are not overweight and for patients who are on their feet a great deal during a typical day.

Twice as nice?

“My personal experience is that both braces and orthotics can be good treatments, and there’s no significant risk to these interventions. But braces can be expensive, sometimes over $1000, and patient copays can be significant,” he said.

But would knee braces and foot orthoses be more effective if they were used in concert? According to a group of Canadian researchers, the combination use of brace and wedge orthoses might provide the most benefit and greatest biomechanical effects.

“Both knee braces and lateral foot orthotics are proposed to help patients with knee OA by lessening medial compartment  loads, but their effects appear to be relatively small and patients frequently stop using them,” said lead researcher Rebecca Moyer, PT, a doctoral student in rehabilitation sciences at the University of Western Ontario in London, Canada. “We hypothesized that by using both orthoses and braces at the same time in this proof-of-concept study, we would see larger overall biomechanical effects.”

In a study e-published by the Archives of Physical Medicine and Rehabilitation in September,⁵ Canadian researchers recruited 16 patients with varus alignment and knee OA, primarily affecting the medial compartment of the tibiofemoral joint. Patients were prescribed a custom-fit valgus knee brace set between 4° and 7°, and instructed to wear it for activities that had caused pain or been troublesome to them in the past. A full-length custom-made foot orthosis was also created using a mold of each patient’s foot. To determine the degree of wedging in the custom orthosis, the researchers had patients stand on prefabricated full-length lateral wedges of varying heights (3 mm, 6 mm, or 9 mm) and assessed the maximum wedge height that would still maintain patient comfort. The unaffected leg was also fitted with an orthotic device with no wedge.

In a biomechanical laboratory, the researchers used 3D gait analysis and an eight-camera motion system to assess each patient walking at a preferred self-selected pace with no device, with the knee brace alone, with the foot orthoses alone, and with a combination of both knee brace and foot orthoses. The researchers then calculated the external KAM, normalized to body weight and height.

They found that the knee brace and wedged orthoses were associated with significant reductions in KAM only when used concurrently. Nine of the 16 patients said they preferred wearing the knee brace and foot orthoses concurrently, while five patients preferred the foot orthoses alone. Only one patient preferred the knee brace alone, and one patient did not like either device.

“Our findings support the concept of combining interventions to get greater decreases in medial compartment loads,” Moyer said.

Moyer noted that the study support the hypothesis that the same overall effects seen with increased valgus angulation of a knee brace or orthotic can be achieved with a smaller—and more comfortable—amount of angulation if both devices are used together. In the study, the effect sizes seen with the concurrent use of the knee brace and wedged orthosis (which ranged from .3 to .4) were comparable to the effect sizes previously reported for knee braces and wedge orthoses used separately. Since the degree of angulation for both the knee brace and wedge orthoses in the Canadian study were determined by patient comfort, achieving an effect size similar to previous studies is particularly significant, Moyer said. Devices that are more comfortable may improve patient compliance and thus produce greater decreases in loads on the knee over time, she added.

Still, further research needs to be performed to validate the Canadian findings before any definitive conclusions can be reached about the relative benefits of each device, Moyer said. However, rehabilitation research with braces and orthotic devices can be challenging because it requires a great deal of time to customize the devices and ensure good fit and data collection.

Moyer also noted that, although KAM is a reliable clinically relevant outcome measure, it is still a surrogate indicator of true medial compartment loading. In addition, most studies of offloading devices are not designed to detect other effects, such as altered distal or proximal mechanics, that may result.

It’s also possible that different subgroups of patients may benefit from different devices, while some subgroups may not benefit from any device.

“We’ve found in our research⁶ that there are patients who are responders and those who are not, but who will best respond to these interventions still has to be defined,” Hubley-Kozey said.

Traditionally it’s been thought that patients who are overweight derive less benefit from these interventions, but that may only be part of the story. For example, response may also vary according to whether a patient has a fixed varus or varus thrust from knee OA, Hubley-Kozey said.

Barbara Boughton is a freelance health and medical writer based in the San Francisco Bay Area.