Roger Federer has revealed the knee injury that sidelined him for two months was sustained as he ran a bath for his twin daughters.

The world number three has not featured since losing to Novak Djokovic in the Australian Open semi-finals, but will make his return at the Miami Open this week after undergoing arthroscopic surgery.

Discussing the circumstances of his freak injury, picked up a day after his defeat to Djokovic, the 34-year-old said: "I remember I turned, I felt my knee was funny, I turned back. That's when I heard a click.

"I did feel that something was strange in my knee. [It was a] very simple movement, probably a movement I've done a million times in my life for sure.

"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.

"One day, two days later I had no more pain. I realised I could already move my leg again. It's pretty incredible to see the progress I've been able to make in a short period of time."

Federer had been expected to return in April but is now preparing to face Juan Martin del Potro in the second round in Miami.

"I'm excited," added the 17-time grand slam champion. "Anxious to find out how it [his 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."