Cincinnati :Fourth-ranked US star Venus Williams, a seven-time Grand Slam champion, withdrew from next week's Cincinnati Open because of left knee pain on Friday with the US Open looming in three weeks.
The five-time Wimbledon winner and two-time US Open champion won at Dubai and Acapulco earlier this year, giving her 43 career WTA titles, but said she dropped out of the harcourt event on the advice of doctors.
"During the last three weeks, I returned to my normal practice schedule and last week began to experience pain in my left knee," Williams said.
"My medical advisors and physio have recommended that I refrain from competition until I am pain free. Unfortunately, I am not at a point where I can commit to competing next week."
Williams' sister, world number one Serena, has already said she will miss Cincinnati and Montreal, the major tuneup events for the US Open, because she cut her right foot on broken glass at a restaurant.
Serena won her fourth Wimbledon title and 13th Grand Slam crown last month and a WTA spokesman said that the injury could jeopardize her participation in the year's final Grand Slam that begins August 30 in New York.
While the Williams sisters will be missing, the other eight women among the world's 10 top-ranked players will compete, including Serbian top seed and world number two Jelena Jankovic and seventh-ranked Kim Clijsters, the reigning US Open champion.