Former World No.1 Caroline Wozniacki has revealed she has been suffering with rheumatoid arthritis for the last few months.
Wozniacki, who won the Australian Open in January, was diagnosed with the auto-immune disease prior to the US Open this summer, but has been able to play through it.
The Dane's 2018 season came to an end as she was knocked out of the WTA Finals at the group stage after a defeat to Elina Svitolina, and she will now use the off-season to plan how to manage the illness, which causes swelling of the joints and fatigue.
She said: "It was a shock. You feel like you're the fittest athlete, or that's in my head, that's what I'm known for, and all of a sudden you have this to work with.
"It's not ideal for anybody, and when you're a professional athlete it's even more not ideal.
"But you find a plan, figure out what to do, you do your research, and thankfully there are great things now that you can do.
"You move on from it and work through it and figure out how to deal and live with it.
"You learn how to cope after matches. Some days you wake up and you can't get out of bed and you just have to know that's how it is, but other days you're fine. You don't feel like you have it.
"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. The medicine now is so amazing so I'm not worried about it. So that's great. You just have to be aware."
Wozniacki did suffer a drop in results after her diagnosis, until winning the China Open in Beijing earlier this month.
Meanwhile, Kyle Edmund's winning run came to an end with defeat by Fernando Verdasco in the second round of the Erste Bank Open in Vienna.
The British No.1 arrived in Austria fresh from winning his first ATP Tour title in Antwerp.
Edmund defeated Diego Schwartzman in the first round but Verdasco proved just the stronger, winning 6-4 3-6 6-3.
The Spaniard had the better of three breaks and held on to take the opening set. Edmund hit back, breaking serve at the start of the second and levelling the match, but one break proved the difference in the decider and Verdasco earned a quarter-final with John Isner or Gael Monfils.
Edmund heads to Paris for the final Masters tournament of the season, which he would need to win to give himself a chance of qualifying for the ATP Finals.