Manager Jurgen Klopp offered an update on his condition after the match, per the Guardian's Andy Hunter:
The Egypt international went down after a heavy collision with goalkeeper Martin Dubravka in the 68th minute at St James' Park with the score at 2-2. He was replaced by Divock Origi.
Carl Markham at the Press Association offered some more details:
The news will be a huge blow to Liverpool at a vital part of the season. Salah had earlier scored his 22nd Premier League goal of the season with the Reds needing a win to go above Manchester City in the title race:
Liverpool play their final Premier League game of the season next Sunday against Wolverhampton Wanderers at Anfield.
However, before then they take on Barcelona in the second leg of their UEFA Champions League semi-final, trailing 3-0 from the first leg at the Camp Nou.
Klopp also confirmed they will be without Roberto Firmino for the second leg against Barcelona.
The Reds will want to have Salah available, as he has been the team's most productive forward since he returned to England last season.
He's a crucial part of the attacking trident alongside Firmino and Sadio Mane, and with limited depth behind the trio, his loss would be a major blow.
Daniel Sturridge has flashed his potential but has had plenty of injury troubles himself, and he lacks the versatility that makes Salah such a special player. Origi helped give Liverpool the lead in the 86th minute, jumping with Jamaal Lascelles before the ball deflected in for a dramatic late goal.