The New South Wales Blues State of Origin five-eighth was injured during last week's game against the Cronulla Sharks, and despite getting through the match, scans have confirmed bad news for Luai, who will miss up to six weeks.
"Jarome Luai was a high-grade injury and will likely miss the best part of six weeks," Head physio Peter Green said on Luai.
"He is currently in a knee brace while the ligament heals and then will move through a process of reclaiming a range of movement, static, then some dynamic strength, then some rehab running and a modified team training phase."
Stephen Crichton may also be racing the clock to return next weekend as he progresses through the NRL's return to play concussion protocols.
He suffered a gruesome ear injury after a head clash with Dale Finucane last week.
The Sharks forward has two-game suspension out of the incident, while Crichton needed plastic surgery. Missing this week, he could miss another game before returning.
"Aside from sustaining a gruesome ear laceration, Critta [sic] had a concussion event and so every precaution will be taken with him as he moves through a strict return to play protocol," Green said.
"He went through plastic surgery on Monday and is at home resting.
"All going well, he will look to be back playing in Round 21 or 22, depending on his progress."
Green also confirmed that Moses Leota is racing the clock to return this weekend, despite being named after suffering a thumb injury in Round 19 and ultimately missing the Round 20 clash against the Cronulla Sharks.
"Moses Leota picked up a thumb injury in our Round 19 game against the Tigers, and despite racing the clock all week to be fit, was unable to take on the Sharks last weekend," Green said.
"He has been back team training all week and will be given right up until the game to prove his fitness."
"Mitch Kenny suffered a Grade 1 MCL injury and will miss one to two weeks depending on how quickly everything settles," Green said on Kenny.