Four-time defending champion Caroline Wozniacki advanced to the semi-finals of the WTA New Haven Open on Thursday but a slight right knee injury put a damper on the celebration. The Danish third seed, who is set to be the eighth seed in next week\'s US Open, defeated Slovakia\'s Dominika Cibulkova 6-2, 6-1 in the quarter-finals and remained unbeaten at New Haven, improving to 20-0. But Wozniacki felt a twinge in her right knee during the first game of the second set and called a trainer. She continued with the knee wrapped and won with ease, improving to 8-3 all-time against Cibulkova, but planned to have the knee examined before deciding if she would play on Friday. Wozniacki is scheduled to face Russian seventh seed Maria Kirilenko, who beat Olga Govortsova of Belarus 6-1, 6-2 in another quarter-final Thursday.