Playing Racket Sports May Worsen Knee OA in Overweight Patients
Racket sports such as tennis and racquetball appear to accelerate degeneration of the knee joint in overweight individuals with osteoarthritis (OA), according to a study presented at the annual meeting of the Radiological Society of North America (RSNA).
Knee OA is a major cause of pain and disability worldwide, affecting approximately 14 million people in the US alone. Excess body weight is a major risk factor. Physical activity offers a host of benefits for people who are overweight, but the wrong type of exercise could potentially increase damage in the knee joint, accelerating the need for total knee arthroplasty.
For the new study, researchers used high-powered MRI to assess the rate of degeneration of the knee joint in 415 overweight and/or obese patients, average age 59, drawn from the Osteoarthritis Initiative, a National Institutes of Health-supported study of individuals with mild to moderate OA (Figures 1-2).
Figure 1. MRI images of a right knee at baseline (A, C) and after 48 months (B, D) for an overweight 47-year-old woman in the elliptical trainer group (A-B) and an overweight 64-year-old man in the racket sports group (C-D). The man in the racket sports group developed severe cartilage damage at the femur and tibia bones (arrows). No cartilage damage was seen in the woman in the elliptical trainer group (A-B). Images courtesy of the Radiological Society of North America.
Figure 2. MRI images of a right knee at baseline (A, C) and after 48 months (B, D) for an obese 76-year-old man in the elliptical trainer group (A-B) and an obese 59-year-old woman in the racket sport group (C-D). The woman developed severe cartilage damage at the femur and tibia bones (arrows), with associated damage of the meniscus (asterisk). No cartilage damage was seen in the man in the elliptical trainer group (A, B). Images courtesy of the Radiological Society of North America.
Study participants kept detailed records of their participation in 6 types of physical activity:
- Ball sports
- Elliptical trainer
- Racket sports
The researchers performed baseline MRIs and then measured changes in the patients’ knees over 4 years using the modified Whole-Organ Magnetic Resonance Imaging Score (WORMS). A higher score indicates more degeneration. Patients regularly participating in racket sports saw their overall WORMS score increase significantly, compared with patients who regularly used the elliptical trainer over the study period. Surprisingly, the overall WORMS score also increased significantly in the racket sports group compared with the jogging/running group. Racket sports participants saw significantly greater degeneration in the medial tibial cartilage compartment. Participants using the elliptical trainer showed the smallest changes in structural degeneration over 4 years.
“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, MD, from the University of California San Francisco and the University of Parma in Parma, Italy.
“We also found that workouts using an elliptical trainer were associated with reduced progression of overall knee joint and cartilage defects. 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 the lowest increase in WORMS sub-scores over 48 months.”
The more-rapid degeneration of the knee joint in people who participated in racket sports is likely due to the high-speed lateral movements inherent to such sports, Dr. Schirò said. These movements can affect the femoral-tibia compartment.
“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,” she said. “In support of this premise, the racket sports group showed elevated cartilage degeneration in the medial tibia.”
The researchers theorize that joint mechanics are impaired in overweight and obese individuals, with a harmful joint overload triggering increased contact stress on the meniscus. Damage to the meniscus compromises the protective cushion on the cartilage of the knee.
“High-impact physical activity with elevated load and high shear forces may trigger and accelerate this process,” Dr. Schirò said. “Moreover, participants who played racket sports showed significantly more meniscal degeneration when compared to the remainder of the study group.”
The data suggest that overweight individuals who continue to play racket sports could slow degeneration in their knees by making modifications to their activities, such as switching to sports with less fast-paced and high shear loads like badminton or doubles tennis.
However, Dr. Schirò emphasized that the degenerative process is complex and individual joint mechanics are highly variable.
“It is possible that some individuals with sufficient strength and motor control may be able to safely play these sports,” she said. “Our data suggest that as a group, though, overweight and obese individuals who play racket sports are at higher risk for disease progression.”
Schirò S, Foreman SC, Posadzy M, Joseph GB, Sverzellati N, Souza RB, McCulloch CE, Nevitt MC, Link TM. Impact of Different Physical Activity Types on Longitudinal Knee Joint Health in Overweight and Obese Subjects: Data from the Osteoarthritis Initiative. Presented at RSNA2020, the106th Scientific Assembly and Annual Meeting of the Radiological Society of North America, November 29-December 4 (virtual meeting).