Kostjasyn, 30, suffered the injury in a pre-season training mishap after joining the Knights at the end of 2016 from North Queensland, where he won the premiership a year earlier.

The Central Coast product suffered narrowed airways despite multiple surgeries.

Kostjasyn played 126 NRL games, beginning his career at Melbourne in 2010.

"Retirement was a combination of medical advice and how my body was unable to adapt to a reduced airway," Kostjasyn said in a statement on Tuesday.

"It has by far been the most challenging six to seven months I've faced, not only in my career but in everyday life.

"Unfortunately, it's a challenge that I've been unable to overcome."

Kostjasyn joined the Cowboys in 2013, playing off the bench in the grand final triumph over Brisbane two years later.

"I'm not over playing footy. I wish I could still run out every weekend, but it's no longer possible," he said.

"As many times as people come and say, throughout your career, ‘It can be all gone in a second,’ everyone sits there and thinks it probably won't happen to me.

"But it does happen to people and unfortunately that's how my career will finish."

Kostjasyn said the injury occurred during a "run-of-the-mill" defensive training exercise in January.

He was initially expected to miss only the first six weeks of the NRL season.

Confirmation his career is over comes a day after fellow hooker Tyler Randell took up a two-year offer to join English club Wakefield Trinity.