Caroline Wozniacki served for the match three times before finally beating Samantha Stosur 4-6, 6-1, 7-5 in the second round of the Dubai Tennis Championships.
The third-seeded Dane led 5-2 in the third set but struggled to close it out.
Wozniacki has been ill with a headache, sore throat and hoarseness since arriving in Dubai, and on the first point of the match a recurring left knee problem surfaced.
After losing the first set, the former top-ranked player took a medical time out to have her knee treated.
"They do say third time lucky, right?'' Wozniacki said. "I was hoping for that.''
Fourth-seeded Ana Ivanovic, out with a broken toe since a first-round exit at the Australian Open, beat Sabine Lisicki 6-0, 6-3, while fifth-seeded Agnieszka Radwanska defeated Caroline Garcia 6-3, 2-6, 6-3.
Also advancing was 13th-seeded Carla Suarez Navarro of Spain, who withdrew from Sunday's final in Antwerp against Andrea Petkovic with a neck injury. Suarez Navarro beat Camila Giorgi 6-3, 6-4.
Three seeded players lost: Petkovic fell to Zarina Diyas 7-5, 6-3; Jelena Jankovic lost to Garbine Muguruza 6-3, 6-4. Peng Shuai was beaten by Tsvetana Pironkova 3-6, 6-4, 7-6.