NEW YORK — American Danielle Collins on Wednesday said she has begun treatment for rheumatoid arthritis, an immune disorder that can cause debilitating swelling and pain in the joints.

The Florida native enjoyed a breakout season in 2019, reaching a career-high ranking of 23rd in the world and reaching the Australian Open semi-finals in January.

"I have not been feeling all that great for quite some time, but it has been somewhat of a relief and completely validating to understand the cause behind my pain," the 25-year-old wrote on Instagram.

"As I have started treatment, I am looking forward to embracing this next challenge in life.

"Without a doubt, every healthy day is a gift and I am one hundred percent committed to keeping strong and continuing to battle on and off the tennis court."

Collins, who is known for her aggressive style of play, said she plans to fight the disease with her trademark tenacity.

"While I don't know for sure what my journey to recovery will be, I do know that I feel really positive about getting back on the court," she said.

"I feel like now I can get better and address my body's needs in fighting this disease."

Collins' primary care physician Dr. Clifton Page said modern treatments can manage symptoms, limit joint destruction and preserve the longevity of active individuals.

"For the elite athlete, rheumatoid arthritis is not a career ending diagnosis," he said in a statement. — Reuters