Williams has won two singles and three doubles titles this year
Venus Williams has revealed she will not play again this year because of a persistent injury to her left knee.
The World number three has been out since 10 September when she lost a US Open semi-final to Kim Clijsters.
"Unfortunately I must continue to keep weight off my knee for the short term and won't be ready to return to competition in 2010," Williams said.
The player will miss the WTA Tour Championships and the Fed Cup finals.
The 30-year-old sprained her left kneecap in early August as she prepared to enter a hard-court championship in Cincinnati.
And the five-time Wimbledon singles champion has been using crutches to keep the weight off of her left leg and undergoing therapy.
She had hoped to play alongside her sister Serena - currently sidelined with a foot injury - in the Federation Cup final against Italy in November.
US Fed Cup captain Mary Joe Fernandez said: "I spoke to Carlos [Fleming, Venus' agent] and learned that Venus is done for the rest of the season with a left knee injury.
"It's unfortunate that Venus is hurt again and won't be able to play in the Fed Cup final."
Williams added: "I am looking forward to returning to full health in time for the start of 2011 season and hopefully having the opportunity to play in both the Fed Cup and WTA Championships next year."