UPDATE 1-Tennis-Serena Williams withdraws from Miami Open with knee injury

Serena Williams has withdrawn from the Miami Open with a left knee injury, tournament officials said on Saturday. It is the second consecutive WTA event in which the American has been unable to continue, after her retirement from last week's tournament in Indian Wells with a viral illness.

"I am disappointed to withdraw from the Miami Open due to a left knee injury," the former world number one said in a statement. "I hope to be back next year to play at this one-of-a-kind tournament in front of the incredible fans here in Miami." (Reporting by Gene Cherry in Raleigh, North Carolina Editing by Ian Chadband)