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Ankle sprains can lead to long-term health problems. Is the brain to blame?

News & Observer - 7/5/2019

Jul. 5--RALEIGH -- At least two million people in the U.S. will sprain their ankles each year. Many will ice the ankle for a few days and then get back to their lives. After all, sprains aren't a big deal, right?

Erik Wikstrom would disagree. As an assistant professor at UNC's Department of Exercise and Sport Science, he's an expert on ankle injuries. He says seemingly innocent ankle sprains can lead to painful degenerative conditions, in part because of how the brain reacts to sprains.

And part of his job is determining how to help the brain and the ankle talk to each other better.

What happens to a sprained ankle?

The most common type of ankle sprain is a lateral sprain, when the bottom of the foot rolls inward. Less common are medial sprains in which the foot rolls outward, or syndesmotic sprains above the ankle.

When the ankle twists, its ligaments--tough connective tissue that holds the joint together--can stretch or tear. The problem is that up to 40 percent of people with sprains seem to develop chronic ankle instability. Having unstable joints can lead to people spraining their ankles over and over again.

"We've seen really strong evidence that links single and recurrent sprains to development of post-traumatic ankle osteoarthritis and degeneration of the ankle," said Wikstrom. Osteoarthritis causes inflammation and stiffness in ankle joints as the cartilage wears away. Since many ankle injuries occur in youth, people in their 20s and 30s can already have degenerative changes to ankle joints, with a huge impact on future mobility and quality of life.

The human brain and ankle sprains

What does the brain have to do with sprains? According to Kimmery Migel, a doctoral student who works with Wikstrom at UNC, quite a lot. Migel noted that joint receptor nerves within the ankle can e damaged during a sprain. These nerves influence the brain's ability to figure out where our body parts are in space.

"How we move is dictated by the patterns that our brain wants us to carry out," Wikstrom said. If the brain can't easily receive signals about where the ankle actually is, it may have less control over the joint. As other areas of the body compensate for the injury, parts of the brain dedicated to controlling the ankle can shrink. The brain can even dampen pathways through the spinal cord to the ankle as communication breaks down.

Wikstrom has a hunch that these changes are driving recurrent sprains. For example, some people with chronic ankle instability tend to put more weight on the outside edge of the foot when they walk. He thinks the brain is seeking information from the foot by stepping harder on nerves that have become less sensitive after a sprain.

This habit--weight on the outside with the sole of the foot rolled in--is the same pattern seen in lateral ankle sprains. Instead of keeping people out of danger, the brain, wanting to know the foot's location, can actually make sprains more likely.

Reuniting ankles and the nervous system

People with sprains shouldn't panic, but Migel explained that even small sprains are a bigger deal than people realize. While ice and rest aren't bad ideas, Wikstrom stresses that at least some form of rehab is necessary.

His research deals with common kinds of ankle rehabilitation to see how the exercises affect neurological functioning. Balance exercises are a standard part of rehab, but Wikstrom noticed that even after training, people were still compensating for their injuries. He wanted to see if adding treatments to balance therapy would improve ankle stability. For his research, some participants receive either massage to the bottom of their foot or manual manipulation of their ankle joints.

The results? It appears that with massage and ankle manipulation, nerve receptors in ankles and muscles are sending more accurate information to the brain. This helps it make better decisions about movement. The benefits seem to remain after treatments are over. His work could help physical therapists find ways to strengthen both muscles and neurological connections.

The study has enrolled over 30 people so far, most of them UNC students, and Migel is actively recruiting more. "If I see someone with an ankle brace I have to stop myself from walking up to them and saying, 'You have a bad ankle, would you like to be in our study?'" she said.

Wikstrom's final advice for sprains is straightforward: "It's not a minor injury. You need to get it treated, and you need to do rehab and exercise for it."


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