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Jury is out on proprioception-OA link

By Barbara Boughton

Despite the awareness among researchers that patients with knee osteoarthritis (OA) have impaired proprioception, the clinical implications of these deficits remain unresolved.

Some scientific evidence indicates that impaired proprioception is linked to increased pain in knee OA, but whether impaired proprioceptive acuity results in progression of the disease remains uncertain. Other questions center on how to best improve proprioception in patients with knee OA, and whether such changes will really influence functional outcomes.

“It’s very clear that there’s impaired proprioception in patients with knee osteoarthritis. But does the impaired proprioception result from the osteoarthritic process or is it a precursor of it? The jury is still out on that question,” said Lynn Snyder-Mackler, PT, ScD, alumni distinguished professor in the department of physical therapy at the University of Delaware. “We also haven’t achieved consensus about whether changing proprioceptive acuity in knee osteoarthritis affects progression or symptoms.”

However, recent research provides some clues about the role of proprioception in the painful symptoms of knee OA, as well as the effects of clinical interventions aimed at proprioceptive deficits.

Large studies that have assessed the interrelationship of impaired joint position sense, pain, and structural damage in knee OA have found that proprioceptive deficits affect the presence and severity of knee pain, and decrease physical function scores, but the effect is modest. Proprioceptive acuity also does not seem to be linked to radiographic evidence of OA or its progression on x-ray.

“Although proprioception is probably an important consequence of the disease, and may be tied to pain and poor balance, its role in the progression of OA is unclear,” said researcher Monica Maly, PT, PhD, an assistant professor of rehabilitation sciences at McMaster University in Hamilton, Ontario, Canada.

Maly’s work indicates that patients’ perceptions of their symptoms and their ability to function—their self-efficacy—is more likely than abnormal biomechanics to influence physical performance on daily tasks.

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Even if the relationship between proprioceptive deficits and clinical outcomes were definitively established, it’s difficult to know what interventions might make a difference. Najia Shakoor, MD, a rheumatologist and an associate professor of medicine at Rush University Medical Center, and fellow researchers have tested an 8-week home exercise program of standard quadriceps strengthening exercises on proprioceptive acuity. They found that although the exercises improved muscle strength and painful symptoms, they did not significantly affect proprioception. Those findings were published in the January-March 2008 issue of the Journal of Musculoskeletal & Neuronal Interactions.

The good news is that many exercise programs that have been shown to improve symptoms and outcomes in knee OA also have the added benefit of improving proprioception, Shakoor said. Yet in the future, research will also need to specifically address the effects of interventions such as exercise on both the frontal and sagittal planes of the knee. In a small study presented in August at the annual meeting of the American Society of Biomechanics, Martha Cammarata, PhD, a research associate at Northwestern University, found that proprioceptive acuity was decreased in both the frontal and sagittal planes in knee OA subjects.

“It will be interesting to see how much reducing frontal plane loading will really improve symptoms and function,” Cammarata said.

Several ongoing randomized controlled trials on proprioception and its effects on knee OA, such as those being conducted by G. Kelley Fitzgerald, PhD, at the University of Pittsburgh, and David Felson, MD, of Boston University, may help clear up the confusion.

“It may be 2012 before we see the results of systematic research that tells us the effects of neuromuscular training programs,” Snyder-Mackler said. “But we do know that what’s likely to work will not be simple. Addressing proprioceptive deficits will mean more than patients doing single leg balance exercises. Patients are also likely to need the feedback of a skilled professional who knows what the appropriate responses should be.”

Sponsored by an educational grant from Ongoing Care Solutions

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