The right-back has left the Reds’ summer tour of the United States and flown back to the UK for an operation after being diagnosed.
He sustained the injury during Liverpool’s first tour match against Borussia Dortmund in South Bend but the extent of the damage was not realised until days later.
Clyne travelled with the squad to their second match in Boston where the reduced swelling exposed the serious damage.
The 28-year-old returned to Merseyside on Monday evening while the rest of the Liverpool touring party arrived in New York.
On Clyne’s injury, Liverpool boss Jurgen Klopp told liverpoolfc.com: “What can I say other than how gutted we all are for Clyney.
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“He was training and playing so well – he was in outstanding shape.
“Clearly an injury of this nature isn’t a happy moment for any player, but the silver lining for him is that, according to the medical guys, it’s a straightforward ACL injury. This means fixing it and coming back from it should follow a path that is free from pitfalls and complications.
“At the moment there isn’t much more to say beyond we’ll all support Clyney in whatever way we can and we look forward to seeing him back on the pitch as soon as responsibly possible.
“He is such a sound professional and is naturally very fit and strong, so all these things are in his favour.”
Adrian Durham on Liverpool's squad
His injury also puts any potential move for Clyne in severe doubt as he begins his rehabilitation process.
Clyne has one year remaining on his contract at Liverpool, who were in talks with a number of clubs about a possible transfer.
Crystal Palace, where Clyne started his career, were tipped to land him as the ideal replacement for Manchester United player Aaron Wan-Bissaka.
Clyne joined Liverpool from Southampton for £12million in 2015, signing a five-year deal.