Williams last played in the Wimbledon final on 5 July

Wimbledon champion Venus Williams has withdrawn from the Rogers Cup in Montreal with tendonitis in her knee.

The American, 28, was forced out of this week's tournament in Los Angeles with the same problem.

Williams has not played since Wimbledon and is now due to return to competitive tennis at next month's Olympic Games in Beijing, China.

World number 12 Daniela Hantuchova of Slovakia has also withdrawn from Montreal due to a schedule change.