Cowboys prop Ben Hannant has announced his retirement effective immediately.

Ben Hannant confirms NRL retirement

North Queensland prop Ben Hannant has confirmed his immediate retirement from the NRL, drawing the curtain down prematurely on a career that included 245 first grade games, 12 Origins for Queensland and six Tests for Australia.

Hannant, who will turn 32 on December 31, had off-season knee surgery where it was discovered that the injury was worse than first thought and he made the unselfish decision to step aside rather than let the Cowboys down.

Reports emerged on Wednesday morning that Hannant had informed the club of his decision to retire but the Cowboys were not able to confirm until he had met with the club doctors and medical staff.

A whole-hearted performer for the Roosters, Broncos, Bulldogs and Cowboys across 12 seasons, Hannant had only signed a one-year extension to remain in Townsville a fortnight ago but took to Instagram on Wednesday to announce that he could no longer keep playing.

"I have been so blessed to play alongside so many great players, coaches, staff, family and fans. Unfortunately it can't last forever," Hannant said.

"I have had amazing opportunities to play at four outstanding clubs and be a part of there (sic) culture.

"To all the players, coaches and staff I'm grateful for your friendship and the great memories.

"And a massive thank you to the members and fans. Without you this could not be possible."

A premiership winner with both Brisbane and North Queensland, Hannant also paid special tribute to his wife Emma and family.

"I want to start by thanking my beautiful wife Emma and my six kids for there (sic) patience, love and support," Hannant said.

"I want to thank my parents for encouraging me to pursue my dreams.

"I'm nervous and excited in what the future holds for my family and I."

Ben Hannant
NRL games: 245 (Won 143, lost 101, 1 draw)
Origins: 12 for Queensland
Tests: Six for Australia
Honours: 2009 Dally M Prop of the Year; NRL All Stars (2011, 2013); PM's XIII (2013)
Clubs: Sydney Roosters (8 games); Brisbane Broncos (148); Bulldogs (37); North Queensland Cowboys (52).