Maria Sharapova pulls out of US Open through injury

Maria Sharapova has withdrawn from the US Open due to a persistent knee injury.

The world number three has been suffering with the problem since Wimbledon, and has not played a competitive match since then.

"I have done everything possible to be ready but it was just not enough time," the Russian wrote on her Facebook page.

The five-time Grand Slam winner's withdrawal comes on the eve of the tournament. She was due to face Australia's Daria Gavrilova in her opening match in New York on Monday.

Sharapova's compatriot Daria Kasatkina will replace her in the draw.