Todd Archer of ESPN reported the news, noting head coach Jason Garrett said the linebacker will not need surgery.
Injuries have been a theme throughout Lee's NFL career. The 2010 second-round draft pick has yet to play a full season since entering the league. In 2018 alone, he suffered a pair of hamstring injuries that collectively cost him a big chunk of the year.
Lee made seven appearances, finishing with 30 tackles and 0.5 sacks.
When healthy, Lee is one of the Cowboys' best defensive players. He was a Pro Bowler in 2015 and 2016, and he earned All-Pro honors in 2016, as well.
But his lengthy injury history means Dallas has grown accustomed to playing without him. Even though Leighton Vander Esch wasn't a direct replacement for Lee when the team selected him in the first round of the 2018 draft, his arrival was a clear reaction to how much Lee's five-game absence impacted the team in 2017.
If the veteran linebacker is forced to miss any game action, the Cowboys will once again look to Vander Esch to assume a bigger role.