Dose-response research refutes the common perception that increasing brace wear time leads to muscle atrophy in patients with knee osteoarthritis. In fact, longer bracing duration appears to improve hamstring strength as well as increasing patients’ physical activity levels.
Pharmaceutical agents have been the mainstay of OA management, particularly the management of OA-related pain. Although pain relief has a positive impact on quality of life, long-term pain medication usage has been associated with an increased risk of tibial cartilage defects and knee OA progression.
Since knee OA is a progressive disease, those with mild to moderate disease have the greatest potential to benefit from conservative interventions aimed at slowing disease progression by altering the biomechanical environment.
Prescription Instructions (or lack thereof):
Part of the reason unloader braces are under-prescribed in the conservative management of knee OA may relate to ambiguity in prescription instructions.
Brace prescription in the research literature has been highly variable, with study participants told to:
“wear the brace as often as possible,” “wear on a regular basis,” “wear for as many hours and for as many days of the week as they wished,” “wear during ambulation,” “wear for bothersome activities,” “wear brace as instructed by physician,” and “wear for prolonged standing and sport.”
In addition to the varied instruction to patients, few studies report the actual duration of brace wear, making it difficult to determine the optimal prescription for benefit, and whether there is an amount of brace wear that may be ineffective or even detrimental.
One area of concern for clinicians is the belief that long-duration brace use will result in decreased muscle strength.
So the question is whether the length of time the brace is worn per day would have an impact on outcomes, and on muscle strength in particular.
The Study & Findings
This study asked 24 patients with Valgus deformities to wear an unloading knee brace “as needed” for 6 months.
Average brace wear duration was approximately five hours per day, but there was a wide range (0-14 hours/day). The study measured pain, function (subjective and objective), and lower extremity strength at baseline and follow up and determined relationships between changes in these variables and duration of brace wear.
Positive relationships were found between duration of brace wear and change in both physical activity and hamstrings muscle strength: the longer the brace was worn, the greater the activity and strength increases. However, the positive relationship between brace-wear dose response and the hamstring strength increase was weak.
What may be more important is that longer brace wear duration was not associated with decreased strength over the six-month follow-up period.
Regardless of how little the brace was worn, perceived pain and function improved, although objective measures of function (walking velocity) did not.
This finding, combined with the positive relationship between brace wear dose and change in physical activity, suggests that there may be different patient-specific strategies for wearing the brace. This study included younger participants with less severe disease than in some other studies, but the brace wear use was varied, with the longer wear times reported for the older patients with more severe disease and less active participants.
The more active people tended to wear the brace less, perhaps only wearing it for specific activities. Conversely, the less active people tended to wear the brace more and the result was an increase in their physical activity levels.
While more dose-response studies are needed to determine the optimal duration of brace wear and the effects of bracing on the mechanical loading environment of the knee joint, the available literature indicates that, in terms of pain, function, activity, and muscle strength, there is strong potential benefit and no harm in wearing the brace as needed, even for prolonged periods of time.
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