Scans show increased knee degeneration in overweight or obese patients who play fast-paced racket sports.
Physical exercise offers a host of benefits to people who are overweight, but not all sports are beneficial. According to new research conducted with MRI, racket sports can actually accelerate knee joint degeneration in this patient group.
Knee joint osteoarthritis affects approximately 14 million people nationwide, and being overweight is a significant risk factor. Despite any associated cardiovascular benefits, a new study to be presented during the Radiological Society of North America (RSNA) annual meeting reveals that racket sports can damage the knee and push a patient toward knee replacement surgery.
“In our study, progression of overall knee joint degeneration was consistently higher in overweight and/or obese patients engaging in racket sports,” said the study’s lead author Silvia Schirò, M.D., with the University of California San Francisco and the University of Parma in Italy.
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Although MRI is the most sensitive imaging method for assessing knee joint structural changes, it has rarely been used to evaluate how different types of exercise affect people who are overweight or obese. But, in this study, Schirò’s team used high-powered MRI to look at the rate of degeneration in the knee joints of 415 patients who were overweight or obese. These patients, who averaged age 59, were plucked from the Osteoarthritis Initiative, a National Institutes of Health-funded study of people with mild-to-moderate osteoarthritis.
Enrolled patients were asked to keep track of their participation in six types of exercise – ball sports, bicycling, jogging/running/elliptical trainer, racket sports, and swimming – for four years. Researchers conducted MRIs at baseline and at the four-year mark using the modified Whole-Organ Magnetic Resonance Imaging Score (WORMS) where higher scores indicate more degeneration.
Based on their analysis, the team saw patients who played racket sports had a significant overall WORMS score increase – even over joggers and runners. Racket sports players experienced the most degeneration in the medial tibial cartilage compartment where arthritis often forms on the inside of the knee.
High-speed lateral movements -- those quick cuts to the side that are common in racket sports -- were most likely the culprit behind the degeneration, the team said. These motions can affect the femoral-tibia compartment, the structure in the knee comprised of the femur condyle – the rounded end of the thighbone that helps it slide over the tibia -- as well as the meniscus.
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“A large lateral force imparted at the foot during side-to-side movements may be driving large knee adduction moments, a key feature in medial compartment disease, which imparts high compressive loads on the medial tibia and femoral condyle,” Schirò said. “In support of this premise, the racket sports group showed elevated cartilage degeneration in the medial tibia.”
It is possible, the team said, that patients who are overweight or obese have impaired joint mechanics and that joint overload can trigger contact stress on the meniscus, damaging that protective cushion on the knee’s cartilage. High physical activity with a heavier load can speed up this process, they said.
On the flip side of these study results, Schirò’s team determined that patients who exercise with an elliptical trainer had the smallest changes in structural degeneration throughout the four-year study period.
“We also found that workouts using the elliptical trainer were associated with reduced progression of overall knee joint and cartilage defects,” she said. “Moreover, our findings showed that when comparing different low-impact activities with each other, such as bicycling, elliptical trainer, and swimming, the elliptical trainer was associated with lowest increase in WORMS sub-scores over 48 months.”
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It is important to note, Schirò said, that the degenerative process in the knee is complicated and can be unique to the individuals. So, some patients who are overweight or obese may be able to continue playing these sports without too much detriment. However, for those for whom it is damaging, there are changes they can make without actually giving up racket sports altogether. They just need to switch to something less fast-paced and has lower shear loads, such as badminton or doubles tennis, she said.
“It is possible that some individuals with sufficient strength and motor control may be able to safely play these sports,” she said. “Our data suggests that, as a group, though, overweight and obese individuals who play racket sports are at higher risk for disease progression.”
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