Researchers say habitual running does not increase the risk of knee osteoarthritis; it may actually protect against it.
The research team, co-led by Dr. Grace Hsiao-Wei Lo of Baylor College of Medicine in Houston, TX, recently presented their findings at the American College of Rheumatology Annual Meeting in Boston, MA.
Osteoarthritis is a joint disease characterized by the breakdown of the cartilage, joint lining, ligaments and bone. It most commonly affects the knees, hips, hands and spine. Around 26.9 million adults in the US are estimated to have some form of osteoarthritis, with middle-aged and elderly individuals being most affected.
Although it is unclear exactly what causes osteoarthritis, some studies have suggested that regular running may contribute to the disease. But the team notes that such studies have been conducted in professional male runners, so they may not apply to the general public.
Furthermore, the researchers note that runners tend to have lower body mass index (BMI), which is associated with lower risk of knee osteoarthritis.
As such, Dr. Hsiao-Wei Lo and her colleagues set out to gain a better understanding of the link between regular running and the risk of knee osteoarthritis.
Analyzing participants from the Osteoarthritis Initiative
For their study, the team analyzed 2,683 participants with a mean age of 64.5 years who were part of an observational study called the Osteoarthritis Initiative. Of the participants, 56% were female and the average BMI was 28.6.
At study baseline, participants were assessed for symptoms of osteoarthritis and underwent knee X-rays. They were also required to complete the Lifetime Physical Activity Questionnaire. This questionnaire pinpoints the most common physical activities a person engages in at four different age ranges in their life: 12-18 years, 19-34, 35-49 and 50 or older.
Knee X-rays were taken again 2 years later and were assessed for signs of radiographic knee osteoarthritis (ROA) - in which the condition shows on X-rays but the patient may not experience pain - using the Kellgren-Lawrence (KL) grade scale. Participants were identified as having ROA if they had a KL grade score of two or more.
In addition, participants were assessed for knee pain. If they had regular pain in one knee as well as ROA, they were classed as having symptomatic osteoarthritis (SOA). Participants who had undergone a complete knee replacement were categorized as having frequent knee pain, ROA and SOA.
Habitual running at any point in life 'is not harmful to the knee joint'
Results of the analysis revealed that participants who engaged in regular running - regardless of the age at which they ran - were less likely to experience frequent knee pain, ROA and SOA, compared with participants who did not run regularly.
Of participants who ran at any point in their lives, 22.8% experienced SOA, compared with 29.8% of non-runners.
The researchers found that individuals with a lower BMI were more likely to engage in regular running.
These results, the team says, suggest that regular running does not raise the risk of knee osteoarthritis among the general population; it may actually protect against the disease.
The researchers note, however, that their study does not determine whether regular running may cause harm to individuals who already have knee osteoarthritis. But Dr. Hsiao-Wei Lo adds:
"However, in people who do not have knee osteoarthritis, there is no reason to restrict participation in habitual running at any time in life from the perspective that it does not appear to be harmful to the knee joint."
Similar findings were reached in another study reported by Medical News Today last year, which suggested that doing up to 150 minutes of moderate physical activity each week does not increase the risk of knee osteoarthritis in middle-aged and older adults.