Australian Open quarter-finalist Danielle Collins has opened up about overcoming endometriosis.

The 28-year-old is set to take on Alizé Cornet in the last eight tomorrow, having come back from one set down in the fourth round to defeat Elise Mertens 4-6, 6-4, 6-4.

Collins, currently ranked 30th in the world, has previously gone far at the Australian Open, reaching the semi-finals in 2019.

This was just one year after she was diagnosed with rheumatoid arthritis, an autoimmune disease that causes painful swelling in the joints.

Collins has overcome yet another health issue to play in this year’s Grand Slam – she underwent emergency surgery to treat endometriosis in April 2021.

"Super-satisfying and rewarding," Collins said of her quarter-final run just nine months on.

"Any time you’re going to have a surgery like I had, I think any athlete would find it nerve-racking knowing how your body is going to recover after that type of surgery. It’s extremely painful and scary."

Endometriosis, which affects an estimated one in 10 women, is an extremely painful condition where tissue similar to the lining of the womb starts to grow in other places, such as the ovaries and fallopian tubes.

This time last year, Collins had not been diagnosed with endometriosis, and doctors were unable to explain why she was in constant discomfort.

This reached a head in January 2021 when Collins was playing against Daria Kasatkina in the semi-finals of the Phillip Island Trophy, an event held at Melbourne Park during the second week of the Australian Open.

Due to severe cramping in her abdominal muscles and pelvis, Collins was unable to serve properly, and lost 6-2, 6-7, 6-1.

Collins told reporters after her victory against Mertens about how much her life had improved since surgery.

“I feel like before [surgery] and before I was on proper medication, I was always having to adjust my training around my cycle because of how painful my periods were," she said.

"And now with things being more consistent, I’m able to kind of train more consistently and not have to have, you know, such drastic changes, especially the week of my cycle."

"I just feel, as a person, more consistent on a day-to-day basis, because I’m not having such terrible fluctuations and such, you know, painful, really just awful days around those periods."

Collins was praised by a reporter for being so open about her struggles with her menstrual cycle. In response, the tennis star revealed she had only received positive feedback about the conversation she had started.

"You know, I had so many other players reach out to me before I had the surgery, during, after," she said.

"And, you know, I think that’s one of the nice things about this sport is I think everyone is very competitive, but I think at the end of the day, I think most of the girls get along with each other really well and are really supportive and very good people."