World number one Serena Williams underwent surgery on her left knee in LosAngeles yesterday and will miss the U.S. Open which starts laterthis month.
"I expect a 100 per cent recovery and Serena's speedy returnto competitive tennis," her doctor, Los Angeles orthopaedicsurgeon Rodney Gabriel, said in a statement released byWilliams's agents IMG.
"It is anticipated that Serena will require six to eight weeks to fully heal. She will not be defending her title at the U.S. Open."
Gabriel said Williams had experienced problems in her left knee for a long time.
"Serena has suffered from quadriceps tendonitis of her left knee for many years, which has been controlled with medication and physical therapy treatments," he said.
"She recently developed pain that, although improved with treatment, increased whenever she resumed tennis activities."
Williams has been out of action since successfully defending her Wimbledon title last month, pulling out of tournaments in Palo Alto, Carlsbad and Los Angeles.
According to the WTA Tour, she is now certain to lose her No. 1 ranking to Belgians Kim Clijsters (No. 2) or Justine-Henin Hardenne (No. 3) between next week and the first week of September.