June 2010

Studies confirm effect of knee bracing on OA symptoms, joint adduction moment

Photo courtesy of MediUSA

But placebo findings raise questions

Three German studies presented at the ISPO meeting in Leipzig confirm that bracing for knee osteoarthritis is associated with both symptom improvement and biomechanical effects. But the findings also suggest that the relationship between those two sets of outcome measures is more complicated than one might think.

In a study of 16 patients with symptomatic medial compartment knee OA, researchers from the German Sport University in Cologne found that 14 days of brace use was associated with significant improvements in pain, stiffness, physical function and total score on the Western Ontario and McMaster Universities (WOMAC) outcome assessment questionnaire.

Similar positive effects were reported by researchers from Bayreuth, Germany, in a study of 33 patients who had suffered from medial compartment knee OA for eight to 10 years. Thirteen patients were randomized to wear an OA brace during activities, two to four hours per day, for 16 weeks. Those subjects experienced significantly greater improvement than a control group of 10 unbraced subjects with regard to pain (as measured using a visual analog scale), four functional measures including WOMAC, and three gait variables (varus/valgus, flexion/extension, and rotation).

The Cologne researchers also found that bracing significantly decreased the net knee adduction moment. A second German study, from Gottingen, analyzed 16 patients with medial knee OA and found that the mean maximum valgus moment provided by the orthosis was 0.053 Nm/kg, which is approximately 9% of the external varus moment (0.63 Nm/kg) experienced by the affected knee while unbraced. The orthotic valgus moment also appeared to affect sagittal plane moments; the Gottingen researchers found that bracing increased external knee flexion moment from 0.23 Nm/kg to 0.33 Nm/kg. Although the external flexion moment for the unaffected knee remained higher, at 0.45 Nm/kg, the symmetry between the two limbs was improved.

The valgus moment applied by the brace likely contributes to the biomechanical and clinical effects. But in the Cologne study, a placebo brace that applied only a minimal valgus moment to the knee was associated with similar effects.

Subjects wore each brace for two weeks, in random order, with a one-week washout period in between. But the placebo brace decreased knee adduction moment and angular impulse, although to a lesser degree than the OA brace. And changes in WOMAC scores from baseline did not differ significantly between the two device conditions.

Similarly, in the Bayreuth study, 10 subjects randomized to wear a soft knee orthosis experienced significant improvment in function, as measured by the Tegner and Insall assessment tools, compared to the control group.

The findings are somewhat consistent with those of a 1999 study published in the Journal of Bone and Joint Surgery by researchers from the University of Western Ontario, in which both a neoprene sleeve and an unloader brace were associated with improvements in disease-specific quality of life and function after six months compared to a control group.

One possible explanation is that the placebo brace gives patients a “perception of stability” that leads to a change muscle contraction patterns, according to Gert-Peter Bruggeman, PhD, director of the German Sport University’s Institute of Biomechanics and Orthopaedics, who presented the findings in Leipzig. To test this theory, Bruggeman and colleagues have conducted a follow-up study using electromyography to assess co-contraction associated with placebo and experimental braces; those data are currently under evaluation, he said.

Research suggests soft orthosis use after ACL reconstruction improves performance

Athletes who have undergone anterior cruciate ligament reconstruction often opt to discontinue brace wear as soon as possible, believing that the device diminishes their athletic performance. But research from Austria suggests that long-term use of a soft knee orthosis may actually have the opposite effect.

Investigators from the University Teaching Hospital in Feldkirch, Austria, analyzed 54 patients who wore a soft knee orthosis for five years following ACL reconstruction. Subjects performed two jump tasks, a simple two leg jump and a “reactive” jump that involved rebounding back into the air after landing. Jumps were performed with and without the orthosis.

During the simple jump task, the orthosis was associated with significant increases in maximum two leg force, force produced by the injured leg, and force normalized to body weight. In the 28 male subjects, it was also associated with significant increases in maximum force produced by the sound leg.

During the reactive jump, the orthosis was associated with significant increases in jump speed, maximum two leg power, power produced by the sound leg, maximum power normalized to body weight, and the Esslingen Fitness Index (power normalized to body weight and age). In the male subjects, it was also associated with significant increases in jump height and power produced by the injured leg.

“The beneficial effects…seem to be larger in more complex movement patterns or sports activities,” said researcher Wolfgang Laube, who presented the findings at the ISPO meeting in Leipzig. “Even if the exact mechanism remains to be elucidated, soft knee orthoses are recommended even years after ACL reconstruction.”

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