Researchers discovered that people with knee osteoarthritis (wear and tear of the knee joint) may have a higher risk of developing Parkinson’s disease later in life. Scientists studied over 21,000 Americans and analyzed genetic data from hundreds of thousands of people to understand this connection. The study found that knee problems were linked to nearly three times higher odds of Parkinson’s disease, but surprisingly, hip arthritis showed no such connection. This suggests that something specific about knee joint damage might trigger changes in the brain that lead to Parkinson’s disease, though more research is needed to understand exactly how.
The Quick Take
- What they studied: Whether knee and hip arthritis (wear and tear of joints) could increase the chances of developing Parkinson’s disease, a brain condition that affects movement
- Who participated: Over 21,000 American adults aged 40 and older from a national health survey, plus hundreds of thousands of people whose genetic information was analyzed to confirm findings
- Key finding: Adults with knee arthritis had about three times higher odds of having Parkinson’s disease compared to those without knee arthritis. Genetic analysis confirmed this connection, though hip arthritis did not show the same link
- What it means for you: If you have knee arthritis, you may want to discuss Parkinson’s disease risk with your doctor and stay alert for early warning signs like tremors or stiffness. However, this doesn’t mean you will definitely develop Parkinson’s—many people with knee arthritis never do
The Research Details
This research used two different scientific approaches to find answers. First, researchers looked at health information from a large national survey of American adults collected between 1999 and 2016, asking people whether they had been diagnosed with arthritis or Parkinson’s disease by a doctor. Second, they used genetic information from hundreds of thousands of people to see if the genes that make someone more likely to have knee arthritis also made them more likely to have Parkinson’s disease. By combining these two methods—one looking at real-world health data and one looking at genes—the researchers could get stronger evidence about whether there’s a real connection between these two conditions.
Using two different methods is important because it helps prove that a finding is real and not just a coincidence. If both the survey data and the genetic data point to the same answer, scientists can be more confident that knee arthritis really does increase Parkinson’s risk. This approach also helps rule out other explanations for why people with knee arthritis might have more Parkinson’s disease.
The study included a very large number of people (over 21,000 in the survey), which makes the results more reliable. The researchers also tested their findings multiple ways to make sure the results were solid. However, the survey relied on people remembering whether a doctor had diagnosed them with these conditions, which could be less accurate than medical records. The genetic analysis used European populations, so results might not apply equally to all ethnic groups.
What the Results Show
In the survey of American adults, people who reported having arthritis were nearly three times more likely to also have Parkinson’s disease compared to people without arthritis. When researchers looked specifically at knee arthritis, the connection was even stronger. The genetic analysis confirmed this finding: people with genes that increase knee arthritis risk also had higher risk for Parkinson’s disease. Interestingly, when researchers looked at hip arthritis alone, they found no significant connection to Parkinson’s disease, suggesting that the knee-Parkinson’s link is specific to the knee joint rather than arthritis in general.
The researchers also tested whether Parkinson’s disease might cause arthritis (the reverse direction). They found no evidence for this, meaning Parkinson’s doesn’t appear to increase arthritis risk. This suggests the connection is one-way: knee arthritis may lead to Parkinson’s, not the other way around. The combination of hip and knee arthritis together also showed a connection to Parkinson’s, but hip arthritis alone did not.
This is one of the first studies to specifically investigate whether arthritis causes Parkinson’s disease. Previous research has noted that both conditions are common in older adults and may share some biological pathways, but this study provides the first strong evidence of a direct link. The finding that only knee arthritis matters (not hip arthritis) is new and suggests researchers need to look more carefully at what’s unique about the knee joint.
The study has several important limitations. People self-reported their diagnoses rather than having them confirmed by medical tests, which could lead to errors. The genetic analysis was done primarily in European populations, so the results may not apply equally to other racial and ethnic groups. The study shows an association between knee arthritis and Parkinson’s but cannot definitively prove that arthritis causes Parkinson’s disease. Additionally, the researchers could not account for all possible factors that might explain the connection, such as physical inactivity or inflammation from arthritis.
The Bottom Line
If you have knee arthritis, discuss with your doctor whether you should watch for early signs of Parkinson’s disease, such as tremors, stiffness, or slowness of movement. Maintaining knee health through appropriate exercise and weight management may be beneficial, though this study doesn’t prove it prevents Parkinson’s. These recommendations are based on moderate evidence and should be discussed with your healthcare provider.
This research is most relevant for people over 40 with knee arthritis, their family members, and healthcare providers treating these conditions. People with hip arthritis alone should not be overly concerned based on this study. Younger people without arthritis don’t need to change their behavior based on this finding.
Parkinson’s disease typically develops slowly over years or decades. If knee arthritis does increase Parkinson’s risk, the effect would likely take many years to appear. This is not something that would happen quickly, so there’s time to discuss prevention strategies with your doctor.
Want to Apply This Research?
- Track knee pain and stiffness weekly using a 0-10 scale, noting activities that make it worse or better. Also monitor for any new symptoms like tremors, muscle stiffness, or slowness of movement, recording when they occur and how long they last
- Set reminders for gentle knee exercises recommended by your doctor or physical therapist, and log completion. Also set monthly reminders to check in with yourself about any new movement-related symptoms and share observations with your healthcare provider
- Create a monthly summary of knee symptoms and any new neurological symptoms (tremors, stiffness, slowness). Share this with your doctor at regular check-ups to catch any early warning signs of Parkinson’s disease and maintain joint health over time
This research suggests a possible link between knee arthritis and Parkinson’s disease risk, but does not prove that arthritis causes Parkinson’s. If you have knee arthritis or are concerned about Parkinson’s disease risk, consult with your healthcare provider for personalized medical advice. This information is not a substitute for professional medical diagnosis, treatment, or advice. Always discuss new health concerns and any changes in symptoms with your doctor before making health decisions.
This research translation is published by Gram Research, the science division of Gram, an AI-powered nutrition tracking app.