Caroline Wozniacki, 28, said she was “shocked” to find out she had rheumatoid arthritis.
The former world number one tennis player was diagnosed with the condition in August this year.
Wozniacki said she sometimes wakes up in the morning and can’t get out of bed.
But her medication is “so amazing”, that she’s not worried about it, and is making a plan on how to live with the condition, she said.
“It turns out that I have an auto-immune disease, rheumatoid arthritis, which goes in and attacks your joints,” said the Dane, who is currently third in the official world tennis rankings.
“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.
“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 to it and do about it.
“You learn how to just 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 live and you’re fine.
“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.”
Rheumatoid arthritis is an autoimmune condition, where the body’s immune system mistakenly attacks the healthy tissue surrounding joints.
It’s the second most common type of arthritis in the UK, after osteoarthritis.
Rheumatoid arthritis is a long-term condition that can cause severe pain in the joints.
The most common rheumatoid arthritis symptoms include swelling, stiffness, restricted movement and extreme tiredness.
Some patients also experience more wide-ranging symptoms, including weight loss, a high fever, or a lack of energy.
These symptoms tend to be worse at certain points – known as flare-ups.
Flare-ups can be difficult to predict, but some treatments may help to reduce symptoms.
Speak to a GP if you’re worried about the signs and symptoms of rheumatoid arthritis.
Diagnosing the condition early is crucial, as early treatment can stop the condition getting worse.
Those most at risk of the arthritis are women, smokers, or people with a family history of rheumatoid arthritis.
While there’s currently no cure for the autoimmune condition, treatment can help to relieve some signs.