Roger Federer says his six-month absence from tennis due to a knee injury could help prolong his playing career.

The 35-year-old Swiss had surgery on his left knee in February and, after missing the French Open with a back injury, announced in July that he needed extensive rehabilitation and would be sidelined for the rest of the season.

Federer returns to action at the Hopman Cup, starting on January 1, which he will play in for the first time since he teamed up with his now wife Mirka in 2002. He will partner compatriot Belinda Bencic, 19, at the international team tournament in Perth.

The 17-time grand slam champion said it was a tough call to take a six-month break and he looked at the bigger picture before deciding.

"I do believe that it could be very beneficial for the future of my tennis career," he told reporters.

"To have had this six-month lay-off, rejuvenated, refreshed ... maybe mentally I needed this rest more than I thought I would. Maybe my body needed a rest more than I thought it would. I tried to look at the big picture, I hope it's going to pay off.

"At least one thing I know now is I have no regrets. I did everything this year to get my body back in shape.

"It didn't feel too gruelling, too long, too hard to go through this process. I have actually enjoyed it."

For much of his career, the former world number one had been blessed with a body that seemed bullet-proof against the aches, pains and injuries suffered by most top athletes.

Until May this year, Federer had appeared in 65 successive majors and the last time he was absent from one of the four majors was at the 1999 US Open.

Roger Federer reached the semi-finals of the Australian Open despite a back ailment. ( AAP: Lukas Coch )

But his semi-final defeat by Canadian Milos Raonic at Wimbledon, which saw him drop to 16 in the world rankings, was his last professional match of 2016.

Federer said his goal was to get fully fit and he was looking forward to a few matches in Perth before the year's first grand slam starts later in the month in Melbourne.

"This year is unique because maybe this is the year more than any time before where I do need matches at the beginning of the season," Federer said, adding he was doing everything possible to add more major trophies to his overflowing cabinet.

"Matches have a different intensity about it and your body reacts according to it."

Federer said he had expected Andy Murray to be world number one at some point but was surprised the Briton finished the year at the top of the rankings ahead of Serb Novak Djokovic.

"That just gives even more credit to Andy for not [just] becoming world number one, but finishing world number one," he said.

"Those are two separate things. Becoming world number one for a week or finishing a year as world number one, it's a different animal."

Reuters