Caroline Wozniacki revealed Thursday that she has been diagnosed with rheumatoid arthritis.

"In the beginning, it was a shock. You feel like you're the fittest athlete out there, or that's in my head, that's what I'm known for, and all of a sudden you have this to work with," Wozniacki told reporters, per CNN.com's George Ramsay. "It is what it is, and you just have to be positive and work with it, and there are ways that you can feel better so that's great."

Wozniacki, 28, made the announcement following her loss to Elina Svitolina at the WTA Finals.

"I think I didn't want to talk about it obviously during the year because I don't want to give anyone the edge or thinking that I'm not feeling well, but I have been feeling well," Wozniacki said, according to Steve Gardner of USA Today. 

She said the diagnosis came before the U.S. Open. The Dane began feeling symptoms of the disease after her elimination from Wimbledon.

Wozniacki told reporters:

"It's something that now I'm happy that I'm done with the season, and you can just kind of control it a little bit more and figure out a plan how to control it even better in the future. 

"Some people can go into remission and some people, it just stops, the disease, and it's just right there and it's not going to get worse, or if it does, it's slowly. The medicine now is so amazing so I'm not worried about it. So that's great. You just have to be aware."

Currently the No. 3 player in the world, Wozniacki said she does not expect the disease to affect her career. She won her first major championship at the 2018 Australian Open and captured the China Open earlier this month, her first victory since the diagnosis.

"I know there are a lot of people in the world that are fighting with this, and hopefully I can be someone they can look up to and say if I can do this, then they can too," Wozniacki said. "And you just kind of have to get together and pull each other up."