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Experts say the starting and stopping in racket sports puts more pressure on the knee joint. CasarsaGuru/Getty Images
  • Researchers say racket sports such as tennis can quicken knee degeneration, in particular in people who are overweight or obese.
  • Experts say the starting, stopping, and twisting in racket sports wears away at the cartilage that protects the bones in the knee joints.
  • They say people at risk for osteoarthritis or other knee ailments should consider sports with less impact such as swimming.

Racket sports such as tennis and racquetball may hasten knee degeneration in overweight people with osteoarthritis, according to new research.

A study presented today at the annual meeting of the Radiological Society of North America found that overweight and obese people experienced significantly higher levels of knee degeneration in racket sports when compared with other sports such as running or swimming.

“In our study, progression of overall knee joint degeneration was consistently higher in overweight and/or obese patients engaging in racket sports,” Dr. Silvia Schirò, the lead study author and a researcher from the University of California San Francisco and the University of Parma in Parma, Italy, said in a press release.

“High impact physical activity with elevated load and high shear forces may trigger and accelerate this process,” she added.

The study hasn’t been published or peer-reviewed yet.

Osteoarthritis is the most common form of arthritis and affects more than 32 million U.S. people.

More than 80 percent of osteoarthritis cases are in the knee. At least 19 percent of adults in the United States ages 45 or older are affected by knee osteoarthritis.

Among the risk factors for knee osteoarthritis are obesity and repeated stress on a joint, like that seen in racket sports such as tennis or racquetball.

“We have known for many years that even in average weight and low weight individuals, the start-and-stop typical lateral movements required in racket sports stresses the knee. Add the extra body weight and knee stress is accelerated,” Walt Thompson, PhD, former president of the American College of Sports Medicine and a professor of kinesiology and health at Georgia State University, told Healthline.

In undertaking the study, researchers used MRI technology to determine the rate of degeneration in the knee joint for 415 study participants who were overweight or obese.

The participants kept records of their participation in 6 types of physical activity, including bicycling, ball sports, jogging or running, elliptical training, racket sports, and swimming.

At the beginning of the study, the researchers did a baseline MRI of the participants’ knees, then measured any changes over a 4-year period.

Those who participated in racket sports regularly had a higher degree of knee degeneration when compared with participants who regularly used an elliptical trainer during the 4 years of the study.

Those in the jogging and running group also saw less knee degeneration than those in the racket sports group.

Those who used the elliptical trainer saw the smallest amount of changes to their knee degeneration during the 4-year period.

Thompson said the results of the study aren’t surprising.

“Weight bearing activities almost always have a higher degree of joint degeneration than non-weight bearing activities,” he said.

“Of the weight bearing activities, if the motion is in one plane (forward or even backward as in running/jogging), acute and chronic injury will be less than activities that require a fast start and fast stop or lateral movements such as in racket sports,” Thompson explained.

“The knee is a hinge joint which is designed to move forward and backward, not to the side. An abrupt lateral movement will cause injury. There is a greater chance of lateral movement in racket sports than in walking, running, or jogging,” he added.

The knee is the largest joint in the body. It’s made up of the upper part of the tibia (shinbone), the lower part of the femur (thighbone), and the patella (kneecap).

Where these bones meet is a covering of cartilage, which protects the bones and offers cushioning when the knee bends.

The meniscus are pieces of wedge-shaped cartilage that play the role of “shock absorbers” in between the thigh and shinbones.

In those with osteoarthritis of the knee, cartilage begins to wear away and there’s less of a protective buffer between the bones. This can cause bone to rub directly on bone.

It’s something Dr. Michael Fredericson, a sports medicine physician at Stanford Health Care in California, sees all the time, particularly for those who play racket sports.

“The sheer force, the twisting, the quick stopping and starting creates this shearing, and that can be very damaging to the cartilage in the knee,” he told Healthline.

Fredericson said there are alternative physical activities that may be better for those at risk of osteoarthritis.

“I tell my patients certainly it would be preferable to do something with less impact… stationary bike, elliptical, swimming. Those are all really good options,” he said.

“If they really like tennis, then I tell them to focus more on doubles because they’re going to have less of that quick starting and stopping compared to singles, so that might be more tolerable for their knee,” he added.

Lynn Millar, PhD, PT, FACSM, a fellow at the American College of Sports Medicine, said options to lessen the extent of knee degeneration include decreasing the intensity and frequency of racket sports, or switching to badminton.

She said pickleball — a sport that combines elements of badminton, table tennis, and tennis — could also be easier for those with osteoarthritis due to smaller courts.

“I still tend to tell people to do what sport they like. If someone is pushed into a sport they do not like, they are less likely to do anything,” Millar told Healthline. “However, supplementary training should be included to make sure they have the proper strength and biomechanics. The individual may need to decrease the intensity or frequency of participation in the sport.”

Thompson said there can be challenges choosing a suitable activity for those who are overweight or obese, but changes can be made to compensate for body weight.

“We know that there is a higher degree of compliance with an exercise program when someone enjoys the activity and sees results,” he said. “Selecting an activity for someone who is overweight or obese can be tricky. However, we generally choose non-weight bearing activities for these clients/patients, then gradually move them to more weight bearing activities as body weight changes.”

“Activities that require abrupt starts and stops or lateral movements are generally avoided because of the stress it imposes on the joints,” he added.