Beijing:Former Olympic tennis champion Lindsay Davenport has pulled out of the Beijing singles tournament with a knee injury, a US official said on Friday.
The 1996 gold medallist has been struggling with the problem since it forced her to withdraw from Wimbledon.
"It's still complications from the knee injury that forced her to pull out of Wimbledon," a team spokesman said.
"There's concern about being able to play potentially 11 matches on it."
Davenport remains in the doubles competition where she will partner Liezel Huber, he added.
The 32-year-old former world number one had spoken about her knee problem, without announcing a pull-out.
"It's doing a bit better. I've been resting it since I hurt it at Wimbledon," she told a press conference on Friday.
"For me it's a thrill to be back no matter what happens."
The six-foot-two-and-a-half (1.89m) Californian is a luminary of the women's game after winning Grand Slams in three consecutive years between 1998 and 2000.
She returned to the circuit in September after giving birth to a baby boy, Jagger, last June.