Despite concerns that running may be damaging to the knee joint, the results of a new study suggest that recreational runners at any age do not appear to contribute to the development of osteoarthritis and may even be protective. The results of the study were presented at the ACR 2014 meeting in Boston. ”In people who don’t have osteoarthritis of the knee, there’s no need to worry about running damaging the knee and limiting their participation in running habits in their lives,” said Dr. Luo of Baylor College of Medicine in Houston. But she stressed that the study did not apply to people who already had osteoarthritis in the knee. Previous studies looking at the link between running and knee osteoarthritis have focused on elite male athletes. To my knowledge, this is the first study to focus on non-elite recreational runners,” Dr. Rowe said in a 2014 ACR news release. ”There is always a concern that running causes osteoarthritis, but Dr. Rowe and others have given runners the results of another data set,” said Dr. Richard, conference chair of the 2015 ACR. Dr. Rowe and her colleagues evaluated 2,683 participants in the Osteoarthritis Initiative (OAI) who were recruited from the community. The average age of the cohort was 64.5 years, the average body mass index was 28.6 kg/ m2, and 56% of the participants were female. 29% of the participants were classified as runners at some point in their lives. All participants underwent a knee x-ray and symptom assessment. They also completed the Physical Activity Questionnaire (modified version), in which they reported the three most physically active age groups, 12 to 18 years, 19 to 34 years, and 35 to 50 years. Four years after joining the OAI, x-rays were used to look for evidence of osteoarthritis. Participants were classified as having radiographic osteoarthritis if they were rated Kellgren-Lawrence grade 2 or higher, and were also evaluated for symptoms of pain. Symptoms of osteoarthritis were defined as radiographic changes in at least one knee osteoarthritis and recurrent knee pain. Individuals who underwent total knee replacement were categorized as experiencing recurrent knee pain, radiographic osteoarthritis, and symptomatic osteoarthritis. Across all age groups, runners had a lower prevalence of knee pain than non-runners (35.0% vs. 41.6%), and the same results were seen in the radiographic osteoarthritis group (53.7% vs. 60.3%) and the symptomatic osteoarthritis group (22.8% vs. 29.8%). After adjusting for age, sex, and body mass index, the results were similar, Dr. Rowe reported. ”Running may prevent the development of osteoarthritis,” she said. However, she further noted that this may reflect a selective bias, as runners are likely to be leaner and eat a healthier diet. “Maybe runners are healthier than non-runners,” she explained. ”There has been a concern, perhaps, that repeated running could lead to osteoarthritis of the knee, but there is little data on that,” said Dr. Robert McLean from the Institute of Geriatrics at Harvard Medical School in Boston. ”This study provides a snapshot of people who participated in the OAI and also reviews their lifestyles and the factors they were exposed to by running. This is the first large population study to focus on this issue, and it helps us understand that high-intensity activity does not increase the risk of knee osteoarthritis,” he explained. ”Focusing on this issue is a great start,” said Dr. McLean, who hosted the WHO press conference during which the data were released.