Using an advanced MRI imaging technique, University of Miami Miller School of Medicine researchers detected cartilage changes in the knees of healthy female runners running a half marathon, in the days following the race.
The study, published September 30 in the Journal of International Medical Research, sets the groundwork for future studies to determine whether these changes are transient, adaptive or eventually lead to knee pain and other problems in runners.
“This study shows that we can take an asymptomatic group of runners and use a sophisticated technology -- MRI T2 relaxation time mapping — to identify changes that we haven’t been able to see in the past,” said study author Lee Kaplan, M.D., director of the University of Miami Sports Medicine Institute, Petra and Stephen Levin Endowed Chair in Sports Medicine, and professor of orthopedics, biomedical engineering, and kinesiology and sports sciences at the University of Miami Miller School of Medicine.
Running exerts four to eight times the force on the lower extremities that walking does. Lower extremity intra-articular cartilage acts as a biological shock absorber in the knee. While prolonged uploading of the cartilage that can occur in running and other repetitive activities is associated with cartilage degeneration, it is unclear and a subject of debate if the continuous pounding from longer distance running has negative long-term consequences on runners’ knees.
Researchers used the MRI technology available at the Miller School to noninvasively detect changes in specific elements that make up cartilage, including proteoglycans, collagen, and water content.
Dr. Kaplan and colleagues -- including co-author Michael Baraga, M.D., associate professor of orthopaedics, director of the orthopaedic sports medicine fellowship, and associate director of the orthopaedic surgery residency program at the Sports Medicine Institute -- collaborated with researchers at the People’s Hospital, Wenzhou, Zhejiang Province, China, to study the knees of six Miami-based female runners. The women were ages 29 to 41-, none were obese based on body mass index measures, and the half marathon was their first or second attempt at the 13.1-mile distance. The women had not run a half marathon in the six months prior to the study. They ran less than 20 kilometers a week and had no previous knee injuries, surgery or knee pain.
Researchers measured biochemical changes in the articular cartilage of each runner’s knee before the half marathon and compared the images to an average six days post-race using the Miller School’s MRI T2 mapping technology.
They detected significant localized cartilage changes on the medial side of the knee post-race compared to baseline. Pre- and post-race T2 relaxation times revealed a significant increase in average T2 values in the outer region of the medial tibia articular surface but no notable increase in the adjacent central region. They also reported a significant decrease in average T2 relaxation time in the lateral femoral condyle central region. The researchers found no significant changes in the runners’ patella, medial femoral condyle and lateral tibia articular surfaces.
“We noticed that the novice runners’ knees were different than more experienced runners that have been studied, in that more experienced runners have a broader area of change than do the novice runners,” Dr. Kaplan said.
The goal now is to find out what those changes mean, if anything, to runners’ knees.
Dr. Kaplan and colleagues plan to conduct a follow-up study with a larger group of male and female runners, as well as look longer term at the impact of potential cartilage changes in the knees of people who continue to run.