Gomez, who joined Liverpool from Charlton Athletic in the close season, suffered the injury while playing for England under-21s against Kazakhstan on Tuesday.
The 18-year-old had made an excellent start to his Liverpool career and began the season as their first-choice left back, putting in some assured displays despite the club's mixed results.
The player underwent a scan on Wednesday with results suggesting he has significantly damaged his anterior cruciate ligament, the Liverpool Echo reported.
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Liverpool's new manager Juergen Klopp can call on left back Alberto Moreno for Saturday's away match at Tottenham Hotspur.
(Reporting by Toby Davis; editing by Alan Baldwin)
