Watson, injured in a Sunday loss to Cincinnati, will undergo surgery at a date to be determined and was expected to make a full recovery, according to the club.
The passer dropped back to throw in the second quarter and fell to his knees without being hit. He was carted off the field and did not return.
Watson completed 63.4% of his passes for 1,148 yards and five touchdowns with three interceptions and ran for another touchdown but was sacked an NFL-high 33 times.
The Browns (1-6) have sputtered offensively all season, never scoring 20 points in a game.
Dorian Thompson-Robinson, Watson's backup, suffered a finger injury and was replaced by Jameis Winston in Sunday's loss, but it is uncertain who will start when the Browns face Baltimore on Sunday.
Watson is in the third season of a five-year contract worth $230 million he signed with the Browns after being obtained from Houston in a March 2022 trade that sent the Texans three first-round NFL Draft choices and two other picks.
Watson sat out the 2021 season after allegations of sexual misconduct in massage sessions and was suspended for the first 11 games of the 2022 campaign and fined $5 million for violating the NFL's personal conduct policy.
He started only six games during an injury-plagued 2023 campaign and underwent season-ending shoulder surgery last November.
