The 21 year-old made his NRL debut in Round 15 this year and played every game since.
“This is a tremendous result for Ryan, who has worked tirelessly in his pursuit of an NRL contract,” said coach Rick Stone.
“Ryan’s form in the NSW Cup and NRL has certainly given the Club the confidence he has a lot more NRL football ahead of him.”
Stig is pleased to re-sign with the Knights.
“As a kid who grew up playing footy in this area, I am really excited to extend my contract with the Knights,” Stig said.
“I am glad my contract is sorted and I look forward to the next few years but my focus is on this season and finishing the year well with my team mates.”