Liverpool defender Joel Matip (32) has suffered a ruptured anterior cruciate ligament (ACL), manager Juergen Klopp told reporters following his side's 2-0 Premier League win away to Sheffield United on Wednesday.
He limped off in the second half of Liverpool's thrilling 4-3 win over Fulham at the weekend, and the injury was diagnosed following a subsequent scan.
British media reported that he was likely to miss the remainder of the season.
"It's an ACL, ruptured - that's unfortunately what I expected from the first second. It looked like that, very unfortunate, but that's it," Klopp told a press conference.
Klopp's injury worries were further increased by a knock sustained by World Cup-winning midfielder Alexis Mac Allister, who had to be replaced in the second half against Sheffield United.