(CNN) When Roger Federer suffered a left knee injury that would later require surgery, the million dollar question was: How did tennis' biggest star get hurt?
Put this one down in the annals of unusual sports injuries: The Swiss speculated that the mishap two months ago occurred while he was running a bath for his six-year-old twin daughters Charlene Riva and Myla Rose, not running down a tennis ball.
The 17-time grand slam champion gave details to reporters Thursday at the Miami Open, his first press briefing since losing to Novak Djokovic in the semifinals of the Australian Open in January.
"It happened the day after the Djokovic match," Federer said. "I woke up. I don't know exactly what happened. I think I was going to run a bath for the girls.
"I made a very simple movement, turned back, heard a click in my knee."
He still, however, went on a family outing to the zoo in Melbourne -- Federer and wife Mirka have another set of twins, nearly two-year-old boys Lenny and Leo.
"Very simple movement, probably a movement I've done a million times in my life for sure," Federer said.
"When I got the news that I had to have the operation, I saw the pictures and talked to my doctor and knew that it was the only way out of this one. In the hospital, when I was about to go into the operating room, that's when I got nervous and sad about it all.
"When I woke up and looked at my knee it was like, 'This doesn't feel like my leg. I can't believe I did the operation and I hope it will come back from here.' That's when I got scared. Then literally one day, two days later I had no more pain."
After the surgery in Switzerland the first week of February -- the first in his career -- Federer said he was on crutches for a dozen days. He had to sit out events in Rotterdam, Dubai -- his second home -- and Indian Wells before coming to Miami. Federer wasn't originally intending to play in south Florida but is seeking matches to get back into the swing of things.
In an enticing encounter, he starts against a friend, the injury ravaged 2009 U.S. Open titlist Juan Martin del Potro on Friday.
"I'm excited," Federer said. "Anxious to find out how (the knee) is going to react. Is it going to be different day-to-day? How is it going to feel after the match? And so forth."
Tennis' equal pay debate resurfaced this week, in the wake of Raymond Moore's controversial comments about the women's game at Indian Wells, with Novak Djokovic having to backtrack on his stance that men's players deserved more than the women after criticism from the likes of women's No. 1 Serena Williams and twice grand slam winner Andy Murray.
Federer's take? He was clear as day.
"I'm all for equal prize money. When I was fighting for prize money increases, especially at the slam level, I was always very aware of the fact that it would impact the women's game," said Federer, a former president of the ATP's player council. "I'm happy tennis has produced some of the greatest female athletes in the world."
His views counter that of a current council member -- and someone who beat Federer at Wimbledon in 2013 -- Sergiy Stakhovsky.
And when asked about Maria Sharapova, who admitted in early March to failing a drug test, the 34-year-old Federer expressed his "surprise" at the revelation from the world's richest female athlete.
Sharapova said she didn't know that meldonium -- which she insisted she had been taking since 2006 -- had been placed on the list of banned substances at the start of 2016.
"I thought she was going to announce retirement or something," said Federer. "But, it also shows that famous players can get caught in the system that seems to be working.
"I know what I take. You have got to be sure. That's why I quadruple check what I take. I don't want to take any chances whatsoever."
Federer has been a supporter of more drug testing in tennis, suggesting in November at the year-end championships that all players should get tested at tournaments from the quarterfinal onwards. He reiterated his stance in Miami.
"I've been in Dubai for 10 years now and been tested once," he said. "That's not okay for me.
"I get tested more in Switzerland because the guy from Switzerland lives in my village. He comes to see me the day after my surgery. In certain countries, maybe the testing is not as serious as in Switzerland. I would like to see that across the board to be the same way and fair. But I think, tennis is doing more and more. I really don't think there is a major problem.
"Tennis is doing a lot better than it has in the past. We're getting more professional. The program is getting bigger and stronger."
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