By Lisa Rapaport
(Reuters Health) - People with knee osteoarthritis who wear stable, supportive shoes for six hours a day may experience less pain than their counterparts who wear flat, flexible shoes, a randomized trial suggests.
Researchers randomly assigned 164 patients with moderate to severe knee osteoarthritis to wear either stable, supportive shoes or flat, flexible shoes for at least six hours a day for six months. For the primary endpoint of difference in walking pain and physical function, the study found no significant difference between the groups.
Stable, supportive shoes did, however, appear superior to flat, flexible shoes for secondary endpoints including pain, ipsilateral hip pain, and knee-related quality of life, researchers report in the Annals of Internal Medicine.
"The findings were somewhat surprising," said senior study author Rana Hinman of the University of Melbourne in Australia.
"Our previous biomechanical research showed that knee loading was lower when people with knee osteoarthritis walked in flat flexible shoes compared to stable supportive footwear," Hinman said by email.
Results from this new trial suggest that there are other factors influencing pain on walking that are more important than knee joint loading, Hinman said. For example, it's possible that the cushioning in stable shoes reduced the impact forces experienced up the leg when the foot strikes the ground, resulting in more pain relief than flat, flexible shoes with minimal cushioning, Hinman said.
"However, further research is required to understand exactly why stable supportive shoes relieve knee osteoarthritis pain more than flat flexible shoes," Hinman added.
For the trial, researchers assessed pain during walking using an 11-point scale from 0 (no pain) to 10 (worst pain possible), with a change of 1.8-units or more considered a clinically important difference. At six months, the mean difference in pain of 1.1 units favored stable supportive shoes, although this difference was too small to be clinically meaningful.
The study results suggest that stable, supportive shoes may be the best option for some, but not all, people with moderate to severe knee osteoarthritis, the study team concludes.
One limitation of the study is the lack of a control group that wore "usual" footwear instead of one of the shoes tested as an intervention in the trial. Another is the selection criteria, which limited enrollment to patients with knee osteoarthritis who were most likely to benefit from the footwear tested in the trial, so the results may not be generalizable.
The study results reflect the idea that shoes alone don't change function in people with knee osteoarthritis, said Dr. Selene Parekh, a professor in the Department of Orthopedic Surgery at Duke University in Durham, North Carolina.
"Personally, these findings are consistent with what I have seen in my clinical practice," Dr. Parekh, who wasn't involved in the study, said by email.
"Flexible shoes are not able to transmit any benefit from the bottom of the foot to the knee, whereas stable supportive shoes seem to benefit the pain experience, but that too, only mildly," Dr. Parekh added.
It's possible that stable, supportive shoes may minimize the awkward mechanics at the knee that can result from walking on uneven surfaces outdoors, and this might be why people in the stable supportive shoe group experienced more improvement in knee pain, Dr. Parekh said.
"I think the take home message is that individuals with moderate to severe knee osteoarthritis should try to wear supportive, stable shoe wear," Dr. Parekh advised. "This may benefit their pain experience as it relates to the knee, but will likely not improve their function."
SOURCE: https://bit.ly/2LecyFR Annals of Internal Medicine, online January 11, 2021.