The 19-year-old flanker was diagnosed with Hodgkin lymphoma shortly after joining the academy in the summer of 2016.
He underwent treatment while continuing non-contact drills and gym work at Castle Park before doctors gave him the all-clear in December 2016.
Jones became an integral part of the academy squad that lifted the BUCS Northern Conference Plate last season and featured in Knights’ three pre-season games ahead of the current season.
He made his competitive debut for the Knights in September’s Championship win over London Scottish.
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Director of rugby Clive Griffiths said: “Sam is a real success story for the club, a fantastic example of local talent coming through the ranks and a player who wants to play for the Knights.
“He has really impressed in his time with us, you wouldn’t think when you watched him playing against Bristol away or Newcastle in pre-season, facing international opposition that he was a 19-year-old learning the ropes.
“I believe Sam will benefit from full time professional training with experienced pros like Michael Hills and Jack Ram as mentors and I’m expecting his game to flourish accordingly.
Academy head coach Ants Posa said: “We are all over the moon that Sam has got his first professional contract with the club.
“Sam has shown that the pathway here at Castle Park is very much working and now our focus is to develop more players to a standard that they can go on to be the next Sam Jones.”