Last updated on .From the section Tennis

Federer says the injury happened the day after he lost to Novak Djokovic in the Australian Open final

Roger Federer says the knee injury he suffered after the Australian Open in January occurred while preparing a bath for his twin daughters.

The 17-time Grand Slam champion, 34, needed arthroscopic surgery to repair a torn meniscus and is set to make his return at the Miami Open this week.

"I think I was going to run a bath for the girls," he said.

"I made a very simple movement, turned back, heard a click in my knee. I went to the zoo. My leg was swollen."

Federer said he was happy with how surgery went but "very sad" he had needed an operation.

"I thought I was going to get through my career without any," said the Swiss. "It was a big shock and, yeah, disappointing."

Federer is scheduled to face Argentina's Juan Martin del Potro in round two in Miami.