Caroline Wozniacki returns a shot to Ying-Ying Duan during their...

Caroline Wozniacki returns a shot to Ying-Ying Duan during their 2013 US Open women's singles match at the USTA Billie Jean King National Tennis Center. (Aug. 27, 2013) Credit: Getty

Sport's most fashionable injuries these days -- concussions and elbow trauma requiring Tommy John surgery -- are virtually nonexistent in tennis. But there is plenty of debilitating pain to go around, from the wrist problem that has knocked defending champion Rafael Nadal out of this year's U.S. Open, to significant back issues that plagued five-time Open champ Roger Federer last year, to past surgeries on women's stars Serena Williams (knee) and Maria Sharapova (shoulder).

Stitched together, the record of tennis-generated infirmities presents clear evidence of the sport's increasingly physical demands. Though a noncontact activity, with genteel country-club roots that originally suggested light exertion, tennis has managed to beat up on the best of its present-day practitioners.

"I had to pull out of Stuttgart [in mid-April] because of a wrist," said Caroline Wozniacki, the former No. 1 player currently ranked 11th. "I hurt my knee in Madrid [early May] and I had to pull out of Rome [the following week]. That's the toughest part about tennis, when you get those injuries that keep nagging."

Two weeks ago, a bum knee forced two-time Australian Open champion Victoria Azarenka to withdraw from the Open tune up tournament in Mason, Ohio -- where she was defending champ -- and added to the physical maladies (before the knee, an ailing foot) that have sidelined her much of the year, causing her No. 2 ranking to plunge to 17th.

Ana Ivanovic -- once No. 1, now No. 9 -- has been playing through discomfort in her back, which radiates pain to her hip, "and it's not something that's going to go out by itself," she said. "Thank God for the Voltaren [a non-steroid anti-inflammatory] that's keeping the inflammation out, and fingers crossed it stays like this."

More than ever, there is a keen awareness of the need for pre-emptive conditioning and stretching exercises to reduce injury risk, and a common presence of physiotherapists as crucial members of players' traveling troupes -- every bit as important as coaches and hitting partners.

"I'm thankful not to be discussing concussions in tennis," said Todd Ellenbecker, an authority on tennis injuries. "That's why we don't wear helmets. But tennis players have lots of problems with the lower back, and we see shoulder, wrist and elbow injuries -- all three of which respond well to nonsurgical treatment."

Ellenbecker is national director of a Scottsdale, Ariz., physiotherapy clinical research group and chairman of the U.S. Tennis Association's sport science committee, so he knows the difference between tennis elbow -- "humeral epicondylitis" to medical insiders -- and the elbow damage that has necessitated so many Tommy John operations in baseball.

"It's not that we've never had a case of tearing the ulnar collateral ligament," Ellenbecker said, "but it is extremely rare."

Even tennis elbow, caused by repetitive stresses not necessarily related to tennis, is not as widespread among the pros as among recreational players, "because it often comes from improper form, or rackets that are too stiff," Ellenbecker said. "From swinging at the ball with the arm and not using the whole body." Nothing like a baseball pitching motion.

In bygone days, when almost everyone hit a one-handed backhand, there were more stresses on the shoulder from that shot, Ellenbecker said. Now, it is the serve and forehand that put demands on the shoulder -- similar, he said, to throwing a football spiral. But the serve, because of the repeated rotation of the body, also strains the lower back and puts pressure on the spine, so that strengthening of the trunk's core muscles are of high priority.

And sometimes physical therapy is not enough. The Open's 2012 champ, Andy Murray, said he had been dealing with back problems "for about two years; I had kind of tried everything. Having surgery for athletes is normally the last resort. But I didn't want to be in pain anymore, so surgery [last year] wasn't actually a difficult decision."

Ellenbecker said that research is not yet complete on whether more hard court tennis, or the sport's expanded emphasis on speed and endurance, have taken an additional toll on players' knees. But the hard-driving Nadal has been the poster boy for knee tendinitis, and he isn't the only one with lower extremity woes.

There is encouragement for the modern-day tennis pro, though, in this statistic: On April 17, the men's pro tour had more 30-and-over players -- 36 -- ranked in the top 100 than any time in history. The oldest was 29th-ranked Tommy Haas, who had just turned 36.

A caution, though: Haas is not playing the Open because he underwent shoulder surgery in June. At least he doesn't have a concussion.

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