Second seed Jelena Jankovic battled through a painful knee injury to overcome Danish teenager Caroline Wozniaki 2-6 6-4 6-2 and reach the fourth round at Wimbledon on Saturday.

The Serb slipped and jolted her left knee at the beginning of the match and appeared in trouble when the 17-year-old Wozniaki, seeded 31, capitalised on a string of errors from her opponent to go a set up.

An early break was enough for Jankovic, 23, to square the match before the Serb took a medical timeout to have her swollen left knee heavily strapped. Wincing after almost every point, a hobbling Jankovic broke to lead 3-1 and, playing on without the strapping, she limped to victory.

World number one and top seed Ana Ivanovic and former champion Maria Sharapova, the third seed, have already been humbled this week.

Jankovic will hope intensive treatment over the next 48 hours will allow her to face Thailand's Tamarine Tanasugarn for a place in the quarter-finals on Monday.

"I hope for the best but you never know with injuries, it's hot at the moment. When I cool down we'll see how it reacts," Jankovic told courtside reporters.

"I slipped at the start of the match. I started to have some pain and I was struggling at the end. Hopefully I will be fine for the next match. The physio said I have probably strained it."

Wozniaki, who reached the second round on debut last year and has risen to 30 in the rankings after a consistent season, will curse her missed opportunity on a sun-baked Centre Court.

The tall and athletic Dane, the 2006 Wimbledon junior champion, used her height to serve to good effect and possesses a solid backhand and scorching forehand.

Jankovic has yet to make the final of any grand slam, but has been a semi-finalist on four occasions.