A new knee injury that required surgery prompted her retirement, reveals Li Na. The 32-year-old Chinese said she began experiencing swelling in her left knee, not the right knee that has previously had three surgeries, and had another procedure in July.

The injury left her being unable to train properly and led her to stop playing, she told the *New York Times*.

"Now the tennis, especially on the women’s side, is really strong. If you want to keep on a high level, you have to keep the body fit," Li said in a telephone interview. "And now I cannot do that anymore, and so I say maybe now is the time because it’s a waste of time if you cannot train 100 percent but still play. This is not myself."

Li now plans to launch various product lines in China, taking advantage of her position as one of the country's most popular sporting personalities, and open an academy for Chinese players, including underprivileged children.