SYDNEY midfielder Isaac Heeney will miss at least a month of training after undergoing knee surgery.

The 21-year-old had been training with the main group since the club's younger players returned to training in late November, but experienced some knee pain and opted for arthroscopic surgery.

Some minor damage to his knee cartilage was repaired and he is expected to return to the main group by late January.

Heeney has battled tendinitis in both knees since arriving at the Swans in 2014, but after a PCL injury limited him to 14 games in his debut season, the gun youngster has played 44 games over the past two years.

He missed the first four rounds of 2017 with glandular fever, but finished the season with career-high averages in possessions (20.6), tackles (4.8) and clearances (3.1) after his first full year spent playing mainly as an onballer and wingman.

Teammates Lance Franklin and Kurt Tippett will also look to step up their training in the new year.

Franklin had minor knee and ankle surgery in the off-season but will join the Swans' main group after the Christmas break, while Tippett is recovering well from an ankle reconstruction and looks on track to be fit to play in the JLT Community Series.