Osteoarthritis, in the simplest sense, is wear and tear of the cartilage (connecting tissue) of the joints, which results in bones rubbing together, causing pain and stiffness. While other factors, such as genetics, can affect the progression of osteoarthritis, the less strain a person puts on his or her joints, the less likely the cartilage is to deteriorate.
With this simple idea in mind, a research team at Rush University Medical Center is testing whether a pressure-detecting shoe insole can help people with knee osteoarthritis walk in a way that reduces the strain on their knees -; and in turn reduce their knee pain and increase their functionality. The study combines the varied expertise of the multidisciplinary team, which includes an engineer, a physical therapist and a rheumatologist who's one of the inventors of a special shoe being used in the study.
Funded by the Arthritis Foundation, the study currently is recruiting men and women past 40 years of age who have osteoarthritis on the inner part of one or both knees (that is, medial osteoarthritis) and who have not undergone knee replacement surgery.
Early intervention may halt osteoarthritis progression
"We know from our studies at Rush that if you have osteoarthritis, and you put pressure on the medial compartment (inside) of the knee too much, the cartilage breaks down faster and the disease can worsen," says Markus Wimmer, PhD, the lead investigator of the study.
"Osteoarthritis is a slow process, it can drag out over many years, so if you intervene early, you can keep it at a certain state so it doesn't progress and become worse," adds Wimmer, who is a professor in the Rush Department of Orthopedic Surgery and the director of Rush's Motion Analysis Lab. "We can't totally reverse it, the cartilage doesn't heal itself, but we can keep it in a stage where it doesn't hurt and progress, where you have options other than to replace the entire joint with an artificial knee."
However, people with knee osteoarthritis tend to walk in a way that puts more pressure on the inside of their knees the worse their condition becomes, creating a vicious cycle of tissue degeneration. "It's contrary to what should happen," Wimmer says. "They don't feel it, because cartilage doesn't have nerves." (The pain of knee osteoarthritis instead results from inflammation related to the cartilage deterioration.)
Walk a mile in their shoes
The research study is testing whether a "smart" shoe insole can help halt this downward spiral. Participants will receive the pressure-detecting shoe insoles and a pair of flat, flexible shoes that allow for natural foot movements for of the entirety of six-week study.
Originally intended for skiers, the insoles are manufactured by a German company founded by one of Wimmer's former graduate students at Rush. Najia Shakoor, MD -; a co-investigator of the study and Professor in the Rush Division of Rheumatology -; was one of the inventors of the shoe, which has been shown to help people with knee osteoarthritis adjust how they walk to put less strain on their knees.
People in the study will walk in both their own shoes and the natural movement shoes in the Motion Analysis Lab -; also known as the gait lab -; where the researchers use three-dimensional motion capture technology to track and measure their leg movements and the pressure of their footfalls. "We can calculate the loads on the inside of the knee joint," says Chris Ferrigno, PhD, MPT, the other co-investigator on the study and an instructor in Rush Medical College's Department of Cell and Molecular Medicine. "Using this technology, we can compare these loads before and after the footwear intervention."
"The shoe itself usually brings a drop in the load due to its design," Shakoor adds. "The insole technology may very well enhance the benefits of the shoe."
Researchers will see if people change how they walk
Following their assessment in the gait lab, study participants will spend six weeks walking in the mobility shoes with the smart insoles inside them and interacting with data that the insoles send to a smartphone. They'll also keep a diary of how often they wore the insole and interacted with it.
After the first three weeks, they'll return to the lab for another set of measurements, then spend another three weeks walking with the shoes and insoles before returning to Rush for a third and final evaluation in the lab. The researchers then will be able to see if and how participants changed the way they walked after training for the previous weeks in the combined shoe and insole.
They'll compare these results with each participant's self-reported pain and function before and after the six-week study period, allowing them to see if changes in how people walked also led to improvements in their condition. "Our ultimate goal is to improve a person's function by directly changing the strains on their knees, which should indirectly reduce their pain," Ferrigno says.
"This could make a difference between progression of osteoarthritis or not," Wimmer adds. "It may stabilize their current condition so they may not need total joint replacement, or delay it for a decade."