Jonny Wilkinson will miss the start of his side's European Challenge Cup campaign after limping from the field in Tuesday night's Premiership clash with Gloucester.
The 29-year-old fly half has suffered a dislocated knee which will rule him for up to three months
Wilkinson underwent a scan on his left knee which confirmed the inury, after initial reports pointed to ligament damage.
Wilkinson will now receive further specialist advice and treatment but is not expected to play much before Christmas.
Falcons director of rugby, Steve Bates, said: "It is obviously disappointing for Jonny to receive an injury just when he was back playing fantastic rugby, but he has enormous strength of character and I am sure he will come back stronger despite this blow."
The talismanic fly-half was seen to twist his knee badly at a ruck midway through the first half and there was immediate concern for the player who has been so often sidelined.
In fact, this was only Wilkinson's fourth game since returning from a six-month spell out with a shoulder injury.
The first game Wilkinson will miss is Newcastle's opening EDF Energy Cup clash at Welsh region the Dragons at Rodney Parade on Friday night.
Newcastle begin their European campaign by welcoming Spanish side Cetransa El Salvador on Saturday, 11 October.
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