Movement Retraining for Osteoarthritis
Can changing the way you walk reduce knee OA pain and improve function?
One of the major risk factors for getting or worsening osteoarthritis in the knee is overloading the joint. Some doctors may recommend weight loss or shoe inserts. Others may suggest a surgical joint realignment called high tibial osteotomy. But researchers are exploring a different approach that focuses on teaching patients to walk differently. This approach is being studied in people with medial, or inner, compartment OA, which is 10 times more common than other forms of knee OA.
“The medial knee compartment bears a much higher load than the lateral [outside] compartment,” says Pete Shull, PhD, assistant professor in the School of Mechanical Engineering at Shanghai Jiao Tong University in Shanghai, China. “That’s just the way our bodies are structured. The inside knee compartment experiences loading [or force] that’s two to three times higher than the outside."
Researchers are looking for ways to shift some of the medial compartment’s load to the lateral one. “The lateral compartment almost always has healthy cartilage,” says Shull, who began his research as a doctoral student at Stanford University. “The compartments are like brake pads on a bike, unevenly worn. So by changing the way someone walks, we can get the cartilage in the compartments to wear more evenly.”
What the Studies Show
In a 2011 study published in the Journal of Biomechanics, Shull and his colleagues retrained nine healthy people without osteoarthritis to shift their gait.
They had the participants walk on a treadmill equipped to measure the forces on the knee.Then they asked the participants to walk again on the treadmill using something called haptic, or touch, feedback. The researchers placed small motor devices on the back of the participants’ legs and backs and instructed them to walk differently, either with their toes slightly in or out, or by shifting their upper body toward an aching knee.
“Whenever they took a step, they felt a buzz, like someone pressing on their back or legs,” explains Shull. “When they felt the buzz, they knew they were supposed to move in that direction.”
With the feedback, people walked in a new way within three to four minutes, as long as they still had the buzzes to remind them when they returned to walking in their old style. The pressure on the medial compartment lessened by 20 percent as compared to a knee brace, which reduced pressure by 10 to 15 percent, and foot orthotics, which reduced pressure by 5 to 10 percent.
Participants repeated lab training once a week for four weeks and practiced the new movement at home for 10 to 20 minutes a day. “We found that after four weeks, people were able to retain the new walking pattern,” says Shull. “After six weeks, people had less knee pain and more function and were still walking in the new way.”
Once Shull and his colleagues established that the technology could help healthy people learn new walking patterns, they decided to test it on people with symptomatic knee osteoarthritis.
In a 2013 study published in the Journal of Orthopaedic Research, the researchers had 10 people with medial compartment knee OA and self-reported pain participate in weekly gait retraining sessions for six weeks. The participants’ walking motions, knee loading, pain and function were evaluated prior to beginning the weekly sessions and one month after completing them.
Using the WOMAC index for the post-training evaluation, participants’ scores for pain and function improved by 29 percent and 32 percent respectively – changes approximately 75 percent larger than the expected placebo effect, the researchers reported. WOMAC, the Western Ontario and McMaster Universities Osteoarthritis Index, is a questionnaire widely used by health professionals to evaluate the condition of patients with OA of the hip and knee.
Shull wants to know if these improvements can be sustained. “We are now working on long-term studies to determine the effect of this treatment several years after implementation,” he says.
Researchers at University of British Columbia and University of Melbourne have also been studying how changes in gait may lessen knee burden. In a 2012 study published in Arthritis Care and Research, researchers asked 22 participants with knee OA to shift the lean of their trunks sideways toward their damaged knee, guiding them to stick to the new walk through biofeedback.
“The amount of trunk lean was measured and displayed in front of the participant as he walked toward a screen,” says study author Michael Hunt, PT, PhD, assistant professor in the Department of Physical Therapy, University of British Columbia in Vancouver. “A target area onscreen guided the amount of lean.”
Although the greater the lean, the less pressure on the inner joint, participants had a tough time learning the new walk and initially at least, found no pain reduction.
Similarly, a 2013 study by the same group, which examined the effects of altering foot progression angles in 22 patients with knee OA, showed no immediate change in knee pain or other symptoms.
“We need three months or more to look at the effect on pain,” says Hunt. “And we also need to see what is going on in other joints. Are we taking the burden off the knee and putting it somewhere else?”
Nor is it clear how much lean is enough, says Hunt. And too much lean, even if terrific for the joint, may not be best for balance.
With movement retraining, scientists are still pinning down terms and ways to measure the load on the knee. And as long as those measurements are uncertain, so are the therapy’s results, says B.J. Fregly, PhD, professor of Mechanical Aerospace Engineering at the University of Florida in Gainesville.
“What is ‘bad load’ on the knee that will cause osteoarthritis to progress?” asks Fregly. “The current theory of what is ‘bad’ is an assumption. And one of the problems too is that we don’t know exactly what ‘bad’ motion is.”
Measuring “load” is difficult because you can’t get inside the joint to do that. It’s done by measuring the external adduction moment, the moment when you put your weight on your leg while walking.
“It’s been shown clinically that people who had the lowest moments after [high tibial osteotomies] had the best clinical outcomes,” says Fregly. “And people who had the highest moment at baseline had the most [osteoarthritis] progression five years later. So there are reasons to believe that ‘moment’ is related to force on the knee.”
Using that “moment” measure, researchers at Stanford found that participants who turned their toes inward reduced their knee load more than those who walked with their toes out or with more sway in their trunks.
Although gait training has been highly individual so far, researchers hope to winnow to a more uniform approach that physical therapists can use without complex measuring instruments or a lab.
“We’re hoping that by the end of our research we can identify movements that will be helpful to most people [with medial knee osteoarthritis],” says orthopedic surgeon Jason Dragoo, MD, associate professor in the Department of Orthopedic Surgery at Stanford, who has been working with Shull and others on gait retraining research.
What Patients Can Do Now
Shull and his Stanford colleagues are currently working to develop wearable equipment to enable real-time feedback about gait patterns that can be used in clinics.
For now, patients can get movement retraining by working with a physical therapist, says Dr. Dragoo: “The physical therapist can help them to walk symmetrically and to spend equal time on both legs, making sure that the trunk is over the legs and not swaying side to side. When you limp, you lose efficiency and that can make knee pain worse.”
What’s most important is to practice the new movement, says Dr. Dragoo: “Once the physical therapist teaches you how to walk differently, you have to be committed to watching the way you walk.”
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