In the moments after I felt the pop in my left shoulder, the sensation I felt was not pain. It was panic. How exactly does a 40-year-old man explain to his wife that he might have torn his rotator cuff during a midnight game of Wii tennis?
Dr. Charles Young made me feel better without even examining me.
Late last year, Dr. Young, an orthopedic surgeon, spent about an hour experimenting with the balance games and strength-training exercises on his new Wii Fit. Running on a virtual trail. Slalom skiing. Walking on a tightrope. "They have this hula-hoop one where you're supposed to spin yourself in a circle and try to get a high score," said Dr. Young, who is completing a sports medicine fellowship at the Cleveland Clinic. "I was really hurting."
In the operating room the next day he commiserated with several nurses who confessed that they had, at least figuratively, already felt his pain.
To say that Wii injuries are an epidemic would be an overstatement, but they are proliferating along with the popular video-game system. Interviews with orthopedists and sports medicine physicians revealed few serious injuries, but rather a phenomenon more closely resembling a spreading national ache: patients of all ages complaining of strains and swelling related to their use — and overuse — of the Wii.
Call it Wii Shoulder. Or Wii Knee. If there is an epidemic of anything, it probably falls under a broader label: Nintendinitis.
"Skateboarding, snowboarding, you name it," said Dr. William N. Levine, the director of sports medicine at NewYork-Presbyterian Hospital/Columbia University Medical Center. "Take the newest fad, and there's always a slew of specific orthopedic injuries associated with it."
The difference now is that the surging sales of the Wii system mean that misery gets more company every day. Nintendo, which introduced the Wii in November 2006, sold more than 10 million of the game systems in the United States last year, including a record 2.1 million in December. The complementary Wii Fit exercise program has been nearly as popular, with more than 6.5 million sold since its introduction last May.
Consumers who avoided sedentary video-game systems have flocked to the Wii, which lures users off the couch with a handheld, wireless remote and a selection of familiar, free-swinging games like tennis, boxing and bowling. For some parents, and even grandparents, the games are a way to connect with children on their own turf. The fact that everyone gets a little exercise along the way is an added plus.
"It's great in the concept that it gets people active and involved," said Dr. Brian Halpern, a sports medicine physician at the Hospital for Special Surgery in Manhattan. "It's not great in that you get lost in that and are overloading areas that you haven't worked out in a long time, if ever."
Dr. Halpern said he had treated two types of injuries: traumatic injuries like twisted knees and sprained ankles from playing the games in confined spaces, and repetitive stress problems from playing too long. A common problem is the realization by players that a full swing is not required; a flick of the wrist is often enough to return a serve or bowl a strike. As several doctors pointed out, that is the exact motion — concentrating the force of a swing in the muscles of the forearm — that can cause tennis elbow.
The Wii system was built with warnings about prolonged use, and electronic prompts interrupt players regularly to urge them to take a break.
Denise Kaigler, a vice president for marketing and corporate affairs at Nintendo of America, said in an e-mail message that "as consumers adapt to this new style of play, there have been a few reports of minor incidents during overly enthusiastic game play," but that more health and safety warnings — about playing in an area free of obstructions, for example — had been added.
"As with any new activity, people playing the Wii system should pace themselves and not overdo it," Ms. Kaigler said.
Dr. John Sperling, a physician at the Mayo Clinic in Rochester, Minn., called the aches and pains a sign of the times. "It's a syndrome of injuries and people presenting with complaints that we couldn't have imagined three years ago," he said.
Dr. Levine said the youngest patient he had treated was 12. Dr. Young, who overworked his core muscles using the Wii Fit, is 32. Dr. Sperling's patients have included a 22-year-old whose arm swelled to twice its size after a marathon Wii session, and a man in his 60s.
"I was asking him what happened," Dr. Sperling said of the older patient, "and he said, 'Well, we bought a Wii system for the grandkids. Next thing I know, my shoulder's killing me.' "
Dr. Halpern, a former assistant team physician for the Mets, compared some Wii injuries to those sustained by professional athletes.
"It's like if you have a pitcher who has gone to spring training and hasn't worked hard in the off-season and starts throwing too much and kind of overloads his shoulder or elbow," he said.
And just as that pitcher might have to take several days off, a person experiencing pain from a session of Wii games should do the same. While "the rush of beating kids a fraction of your age in Wii Sports far outweighs the discomforts of getting older," Ms. Kaigler said, moderation is just as important. That may be especially true for older players.
My shoulder recovered with time away from the Wii, not a problem in a household with three children who were all eager to play and who are apparently more durable than their father. The lasting image of Christmas at my family's home was that of my 5-year-old daughter in a velvet dress, blond hair tucked behind one ear, raining punches on a hulking man with a goatee. She knocked him out, but quickly moved on to baseball and bowling and golf.
Dr. Halpern said the shorter attention spans of younger children were probably preventing them from developing overuse injuries, describing their exposure to a variety of Wii games as "cross-training without even thinking about it." Sore-shouldered and gimpy-kneed adults could be victims of their better focus, but also of their innate competitiveness.
"It's good to be a kid at heart," said Dr. Susan Joy, the director of the Cleveland Clinic's women's sports health program. "But sometimes when you start a new exercise program, it's good to remember that you're not a kid."