He would be eligible to return for the Christmas Eve game against Denver in Week 16.
Lynch suffered the injury during the Raiders' Week 6 loss to the Seattle Seahawks in London. He was trying to pull his right leg out of the grasp of Seahawks cornerback Shaquill Griffin when linebacker Austin Calitro leveled Lynch, who landed awkwardly and stayed on the Wembley Stadium pitch for a moment before gingerly jogging off the field.
Lynch, 32, has rushed for a team-high 376 yards on 90 carries (4.2-yard average) and three touchdowns in 2018. He also has 15 receptions for 84 yards.
The five-time Pro Bowler's two-year contract is up after this season; it pays him a fully guaranteed $2.5 million in base salary after he restructured it this offseason, though it carries a salary-cap number of more than $4.45 million for 2018, per ESPN Stats & Information data. Lynch received a $1 million roster bonus on the 11th day of the league year, and he already has accrued $281,250 in roster bonuses ($46,875 per game on the Raiders' 46-man roster, with a max of $750,000). He would miss out on $468,750 in bonuses if he did not play another game this season; he stood to earn up to $3.75 million in yards and touchdown incentives.
ESPN's Paul Gutierrez contributed to this report.