Patient Evaluation of An Unloader Knee Brace: A Prospective Cohort Study

Karen K. Briggs
MPH Lauren Matheny
A J. Richard Steadman
MD Steadman Hawkins Research Foundation, Vail, Colorado

Introduction

The prevalence of osteoarthritis (OA) is constantly increasing, currently affecting 4.3 million adults in the United States, and making it the most prevalent of the chronic joint disorders worldwide. One contributing factor that may increase the severity of knee OA is knee malalignment.⁸ Sharma et al. showed that a compartmental increase in the load of the knee can cause an increase in knee degeneration of that compartment.¹²

Many nonsurgical and surgical treatment options exist that may relieve pain, and therefore increase knee function. Non-surgical treatment options include oral supplementation, such as glucosamine and chondroitin, and corticosteroid and hyaluronic-acid knee injections. Previous studies have shown that oral supplements as well as intra-articular injections may cause a decrease in symptoms such as pain; however, these treatments are temporary and do not change the mechanics of the knee.⁹

Some surgical treatments have been developed to treat malalignment of the knee; however, these procedures are quite invasive and require lengthy recovery times and rehabilitation. And though these operative procedures, which are intended to relieve knee pain by reducing the weight bearing load in the degenerative compartment, are available, there is an increasing desire for non-surgical treatments that address the issue of malalignment.³

Unloader braces are specifically designed to decrease the load on the degenerative compartment of the knee in order to improve function and decrease symptoms related to malalignment and OA.^7, ¹⁰ The purpose of this study is to document patients' expectations of treatment and outcomes following six months of use of an unloader brace. Outcomes and response to the brace were measured by symptoms such as pain and stiffness, function, use of pain medication, and quality of life.

Methods

Patients were enrolled in an IRB-approved prospective cohort study. Excluded were patients who had any arthroplasty in the knee, or moderate to severe OA in both lateral and medial knee compartments. Inclusion criteria were diagnosis of osteoarthritis of the knee with unicompartmental knee conditions that required load reduction to the affected compartment and a minimum of a six-month prescription in order to allow for sufficient trial of the brace. Patients signed informed consent forms and agreed to complete all mailed questionnaires. At enrollment, three weeks, six weeks, and six months, patients completed a self-administered questionnaire. This questionnaire included the SF-12; the WOMAC score¹; and a survey of patients' use of both prescription and non-prescription anti-inflammatory drugs. In addition, all patients completed an expectation questionnaire prior to enrollment in the study. Twenty patient expectation domains were measured. The domains were then analyzed individually as "very important" to "of little to no importance." These data were then summed as an expectation score with a range of 20�80, 80 showing no expectation and 20 showing the highest expectation.

Statistical Analysis
Comparisons of scores between pre-brace WOMAC and final time point (six months) were performed using the paired t-test. Comparisons between independent groups were performed using the independent t-test. We used repeated measures analysis to determine if there was a difference between pre-brace, three-week, six-week, and six-month WOMAC pain and function scores. Because the WOMAC scores were assessed on the same patient over time, we used repeated measures analysis to adjust for the within-patient factors.

Results

Thirty-nine patients were enrolled in this study. The average age was 60 years (range 44 to 87). Average body-mass index (BMI) was 26 (range 20 to 37). There were 22 men and 17 women. Twenty-five patients were prescribed a medial unloader brace, and 14 were prescribed a lateral unloader brace. Seven patients (18 percent), five women and two men, discontinued brace wear.

Patient Expectations
Pain relief was very important to only 69 percent of patients and somewhat important to 17 percent. If patients did expect pain relief, 39 percent expected most of the pain to be relieved, and 57 percent expected all pain to be relieved. Seventeen patients (37 percent) also reported stiffness as a primary reason for seeking medical treatment. Eighty-six percent of the patients expected knee stiffness or swelling to stop. Improving their ability to walk was considered very important by 89 percent. Of those who considered walking important, they all expected to walk more than one mile. Improving their ability to go up and down stairs was considered very important to 70 percent. Patients considered return to recreational sports an important expectation. It was considered very important to 83 percent and somewhat important to 17 percent. The most important expectation in this group was to have confidence in their knee (97 percent very important), avoid future degeneration of their knee (90 percent very important), and improve ability to maintain general health (93 percent very important).

The WOMAC scores are shown in the following table. There was significant improvement in pain, stiffness, and function components of the WOMAC score (p<0.05). Patients also had a significant improvement in their quality-of-life physical component as shown by the SF-12 (p<0.05). As expected, the patient mental component of quality of life remained unchanged.

At three weeks, 24 percent of patients reported a decrease in over-the-counter anti-inflammatory use, and 16 percent reported a decrease in prescription anti-inflammatory use. At six months, 23 percent reported a decrease in over-the-counter anti-inflammatory use and 16 percent reported a decrease in prescription anti-inflammatory use.

Discussion

In this population, patients expected pain relief, improved function, and improved activity level. It was very important for the patients to avoid future degeneration of the knee and to be able to maintain their general health. The unloader brace decreased pain in the initial weeks following bracing and maintained improvement throughout the study. Improved patient function and a decrease in stiffness were also seen in the initial weeks and were maintained at end point as well. Patients reduced medications and had improved overall physical health.

The results of this study are similar to those of Kirkley et al.⁷ In the Kirkley et al. study, there was a control group, a neoprene-sleeve group, and an unloader brace group, all of which consisted of patients under 50 years old who had a BMI of less than 35. Patients who used the unloader brace showed less pain than the other two groups after walking for six minutes and climbing for 30 seconds. They also showed a significant increase in quality of life and knee function. And although not significant, there was a strong trend toward a significant difference between the unloader group and neoprene-sleeve group regarding the overall WOMAC score and the functional component of the WOMAC.⁷

Other studies have also shown unloader braces to be effective in not only reducing symptoms, but also in shifting the weight-bearing load.^{2,4�6,10�11} Self et al. showed a significant decrease in varus moment during stance, which can contribute to a reduction in pain.¹⁰ And Pollo et al. showed a shift in the center axis of pressure with the use of an unloading brace. Resting pain, night pain, and pain with activity all showed a significant decrease with brace use.¹¹

In this patient population, the mean BMI was quite low, which may not be representative of a normally distributed population. Also, many of the patients in this study had a low pre-brace WOMAC score, which may not have allowed for as much improvement.

Overall, patients demonstrated a significant decrease in pain and increase in function and overall physical health. Braces specifically designed to unload the degenerative compartment of the knee may be an effective treatment for pain generated from OA in conjunction with malalignment of the knee.

This research was funded in part by Ossur Americas, Aliso Viejo, California. Address correspondence to Karen K. Briggs, MPH; Steadman Hawkins Research Foundation; Attn: Clinical Research; 181 W. Meadow Dr. Ste. 1000; Vail, CO 81657.

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