He will be further evaluated Sunday, the team said.
Lynn limped off the field after a pitch during the fourth inning against Arizona. The 34-year-old had issues with the same knee last season and went on the injured list for 10 days. He also spent almost a month after the season resting and rehabbing the knee.
Lynn's injury comes hours after Chicago announced that left-handed reliever Garrett Crochet will need season-ending Tommy John surgery.
The 22-year-old Crochet had a 2.82 ERA over 54 appearances last year, going 3-5 with 65 strikeouts in 54 1/3 innings.