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Neutral bracing produces more stability in medial knee OA cases than valgus bracing
Medial muscle co-contractures in study subjects diminished more with neutral than valgus bracing.
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A study conducted at the University of Delaware and funded by the National Institutes of Health comparing two styles of knee bracing in subjects with medial compartment osteoarthritis showed that neutral bracing produced results as good as or better than valgus brace alignment.
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However, neutral braces were more straightforward to use, which in the long run might mean greater overall cost savings because a simpler neutral-alignment double-upright style brace may then be used, according to investigators.
More importantly, neutral braces applied fewer forces to the knee, thus enabling wearers to perform more activities of daily living (ADL) pain-free, said Lynn Snyder-Mackler, PT, ScD, FAPTA, the study’s senior author.
These findings suggest such braces potentially could help an ever-increasing number of people with medial knee osteoarthritis (OA) with a wider range of body types, especially those who are not candidates for unloading osteotomies, she told Orthopedics Today.
Fewer co-contractures
Snyder-Mackler and co-investigators theorized that medial muscle co-contraction might have originally increased joint compression in subjects they studied, but the bracing subsequently diminished co-contraction, produced less pain and afforded subjects increased ability to perform ADLs, such as walking symptom-free.
“What we found was a decrease in co-contraction — a decrease in symptoms — no matter which brace they used, whether it was in neutral or the brace was in valgus,” Snyder-Mackler said.
The neutral brace effectively eliminated any wobble in the knee and increased overall stability. “So, effectively it unloads them because they’re not compressing the joint with the muscles,” she said.
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Image: Snyder-Mackler L |
Although the study only included a few subjects, Snyder-Mackler maintained her confidence in its outcomes, saying they were likely reproducible in a larger study.
Surveyed three times
The study included 17 subjects with medial compartment OA, intact ACLs and genu varum (54.5 ±8.8 years old; BMI 30.9 ±4.1 kg/m2). All subjects were fitted with a GII Unloader Brace (Ossur).
At three separate time points, investigators surveyed subjects about their ADLs with the self-reported Knee Outcome Survey (KOS), checked gait, kinematics and kinetics, and evaluated muscle function during walking. This was done without the brace, while subjects wore their braces set at 0° and set at 4° valgus.
There was a 2-week washout period between the two bracing sessions.
Expanded applications
Knee function scores were lowest with the knee unsupported, based on the KOS and Knee Osteoarthritis Outcome Score. They were the highest with the knee in neutral.
Investigators theorized that subjects may only have scored well initially when unbraced because over time, they gradually self-limited their activities without realizing it. In fact, many of the patients, after being braced for the study, later reported decreased activity levels and increased OA symptoms without bracing.
“Once they were braced, they realized they could do lots of things without pain,” Snyder-Mackler noted.
A big advantage to neutral braces is that the straps and increased forces incorporated into the valgus brace design – all of which are meant to better align the knee – can be eliminated with little impact on the outcome, she said.
“That should also translate into it being able to be used on a larger variety of body types … and so maybe an off-the-shelf brace would work,” she added.
The findings were presented at the International Society of Arthroscopy, Knee Surgery and Orthopaedic Sports Medicine Congress. Collaborators included Michael J. Axe, MD and Dan K. Ramsey, PhD.
For more information:
- Lynn Snyder-Mackler, ScD, PT, SCS, can be reached at the Department of Physical Therapy, University of Delaware, 309 McKinly Laboratory, Newark, DE 19716; 302-831-8667; e-mail: smack@udel.edu. She has no direct financial interest in any products or companies mentioned in this article.
References:
- Ramsey DK, Axe M, Snyder-Mackler L. Effect of valgus bracing on muscle function in medial knee OA. #260. Presented at the 2007 International Society of Arthroscopy, Knee Surgery and Orthopaedic Sports Medicine Congress. May 27-31, 2007. Florence.
- Ramsey DK, Briem K, Axe MJ, Snyder-Mackler L. A mechanical theory for the effectiveness of bracing for medial compartment osteoarthritis of the knee. J Bone Joint Surg Am. 2007; 89:2398-2407.