McManus is proudly a one-club player who made his NRL debut in 2007 and went on to play 166 games for the Knights, scoring 72 tries.
Injury had sidelined the 30-year-old indefinitely this season, before he was medically advised to call fulltime.
“It is obviously a difficult decision but a decision I made for my young family,” McManus admits.
“I could never have dreamed that when I moved from the Northern Territory to Newcastle, that I would have got to play one game let alone playing the game I love for ten years.
“I am very privileged to have played my whole career at the one club and I am very honoured to have worn the Newcastle Knights jersey.”