Williams sisters out of Charleston event

CHARLESTON, S.C., April 7 (UPI) -- Sisters Venus and Serena Williams, who have been hampered by injuries this season, withdrew Friday from next week's Family Circle Cup in Charleston, S.C.

Venus has a right-elbow sprain. Serena, who is 2-1 this season, is hobbled by a left-knee injury.

"I am very disappointed to have to withdraw from the Family Circle Cup due to ongoing pain in my left knee," Serena said on her Web site. "I know that the Family Circle Cup will host another incredible event this year and I look forward to playing in Charleston again next year."

Venus Williams was injured during her three-set, first-round loss to Tszvetana Pironkova at the Australian Open in January.

When the Family Circle Cup begins on Monday, the field will include four-time Grand Slam champion Justine Henin-Hardenne, Svetlana Kuznetsova of Russia and Switzerland's Patty Schnyder.