BEIJING (Reuters) - China's Li Na, Asia's only grand slam singles champion, announced her retirement from tennis on Friday, succumbing to the effect of long-term knee injuries.
A former French Open winner and the reigning Australian Open champion, Li said her troublesome knees, that have plagued her throughout her career, prevented her from ever regaining full fitness and forced her hand.
"The task of finally making a decision to hang up my racquet felt a lot more difficult than winning seven matches in a row in the Australian heat," she said in a letter posted on her Facebook page.
"It took me several agonizing months to finally come to the decision that my chronic injuries will never again let me be the tennis player that I can be.
"Walking away from the sport, effective immediately, is the right decision for me and my family."
The 32-year-old, known affectionately as "Big Sister Na" and "Golden Flower" in China, won the 2011 French Open then this year's Australian Open.
She climbed to number two in the world rankings but her knees were steadily getting worse and she skipped this year's U.S. Open, triggering speculation her dazzling career was drawing to a close.
"Most people in the tennis world know that my career has been marked by my troubled right knee. The black brace I wear over it when I step on the court has become my tennis birth mark. And while the brace completes my tennis look, the knee problems have at times overtaken my life," she said.
"After four knee surgeries and hundreds of shots injected into my knee weekly to alleviate swelling and pain, my body is begging me to stop the pounding."
One of the most popular and marketable players on the tour, news of her retirement set off a flood of tributes.
The Chinese Tennis Association, in a statement released by the official Xinhua news agency, said it respected her decision and wished her the best.
"We also thank Li Na for the passionate and proud, shining moments she gave to Chinese tennis in her competitive career," it said.
Top tennis players posted notes to her on their social media accounts. Caroline Wozniacki wrote: "Li Na, one of the funniest and nicest players on tour! A great competitor and a role model both on and off the court! You will be missed!! An exciting new chapter starts today!"
Nowhere will her retirement be felt more than in her homeland, where she has inspired a generation of young Chinese tennis players and brought the professional game to her country.
For many young people in China, Li is a role model, with her steely determination, broad smile and English language skills emblematic of a confident and rising country.
Sport and politics remain tightly woven in China, where elite athletes are handpicked from a young age to be nurtured by the state. Only a handful are allowed to manage their own careers.
Li, who was identified as a potential badminton talent as a child, was steered into tennis before her teenage years, but had to be coaxed back into the game in 2004 after walking away to study media at university.
Despite growing adulation from her success, including becoming China's first WTA title-winner in 2004 and first grand slam quarter-finalist at Wimbledon two years later, Li has proved a reluctant standard-bearer for Chinese tennis.
After numerous clashes with local media and Chinese tennis authorities over training routines and pay, in 2009 the strong-willed Li was permitted with four other top women to manage her own career and keep a greater share of her winnings.
China has a history of placing enormous expectations on athletes who have reached international acclaim and each live broadcast is usually viewed as a barometer of global standing or national pride.
In 2008, when defending champion Liu Xiang was forced to drop out of the 110 metres hurdles at the Beijing Olympics due to an injury, his withdrawal was met with tears, anger and accusations that the athlete had let the nation down.
Li is among a handful of top women players whose success in an individual game inevitably conflicted with their country's Soviet-style sports system.
Shortly after returning to training from two years out of the game, she won her country's first WTA tour title on home soil in Guangzhou and two years later was in the quarter-finals at Wimbledon.
During her career, she won nine WTA events, including the two grand slam titles, and reached number two in the world rankings.
She earned more than $16 million in prizemoney and much more in endorsements and sponsorship. Earlier this year, Forbes listed her annual earnings at $23.6 million, making her the world's second highest-earning female athlete.
Stacey Allaster, the WTA Tour chief executive, said: "It's hard to be a household name in a nation with 1.4 billion people, but that's what Li is."
Reporting by Ben Blanchard, Li Hui and Hou Xiangming