GEELONG defender Lachie Henderson will be in main training sometime in January after undergoing off-season knee surgery.

Henderson had an arthroscope on his knee at the end of the 2017 season and will begin his pre-season on a reduced training program. 

"I'll be back in main training by January by the time I get it all sorted," Henderson told AFL.com.au. 

"There'll be a few of us coming back in January and we'll be ready to go. 

"I can do most things. I'm running pretty freely, so the base fitness is pretty good." 

Henderson has not been cleared to join in any football drills just yet, but importantly he has the green light to complete his running program.

The star defender is confident the surgery won't affect his preparations for the 2018 season too substantially.

"It was a bit of wear and tear. It wasn't really a set injury, it's just a bit of wear and tear over the 10 years I've been playing," Henderson said.

"Nothing too serious but I've just got to work through it." 

Henderson said having Harry Taylor back in defence, with the veteran swingman set to resume his duties in the backline in 2018, would be a major fillip for a young backline. 

With Tom Lonergan and Andrew Mackie retiring, inexperienced defenders Jed Bews (50 games), Jake Kolodjashnij (47 games), Tom Stewart (21 games) and Zach Guthrie (nine games) will be vying for a place in the backline. 

Henderson, Taylor and Zach Tuohy will be charged with leading a backline that has lost 489 games of collective experience following Lonergan and Mackie's departures.

"It'll be different, we've got a young group down there again," Henderson said. 

"Harry will come back and do his thing. He's a gun. But we lose a lot of experience with 'Domsy' (Lonergan) and 'Mack' (Mackie) going. 

"Getting those young boys in there and giving them an opportunity down there, I think we'll be better for it." 

Going into his third season with the Cats, after two seasons at the Brisbane Lions and six at Carlton, Henderson is playing some of the best football of his career. 

Henderson said being settled in Geelong was an important factor in the consistent football he has been producing.

"I'm loving the club and being down here and playing with some of the players that I have done over the last few years," he said. 

"We've got a pretty good group together right now so hopefully we can keep improving."