McKinnon, 22, had emergency surgery early on Tuesday morning in Melbourne to stabilise his neck following a lifting tackle by three players in Monday night's NRL defeat by the Storm.
The surgery consisted of a disc removal at C4 and C5 and anterior fusion.
"He's been in an induced coma just to help with the recovery from the surgery and to make sure there is no movement there," Knights chief executive Matt Gidley told News Corp Australia.
"The scans showed the spinal cord was not cut but they are still determining what damage might have been done there. It's just a real anxious time at the moment."
Knights coach Wayne Bennett said the club would give McKinnon all the help he needed to recover.
"It's sad and extremely disappointing for him. There is not much we can do about it," Bennett said.
"He is getting the best care now and we are giving him all the support we can possibly give him. After that we just have to hope for the best.
"It's tough on all of us. This kind of thing doesn't happen."
The veteran coach, who took McKinnon with him to Newcastle from St George Illawarra when he moved to the Knights in 2012, admitted he was struggling to get his head around what had happened to a player who had been tipped to represent NSW.
"It really does bugger your mind up," Bennett said.
"He is an outstanding young man."
The incident shocked the NRL community, with players from various club taking to social media to express their best wishes towards the NSW Country Origin representative.
Storm prop Jordan McLean's lifting tackle that led to McKinnon's injury was referred straight to a judiciary hearing which has been deferred.
The match review panel on Tuesday announced McLean had been charged with a dangerous throw for his part in the tackle alongside teammates Jesse and Kenny Bromwich and it would go to a hearing because of the serious injury that arose.
