The injury explains why Bennett, who left the Tampa Bay Buccaneers this offseason to join Seattle, received a one-year contract from the Seahawks. The deal is worth $5 million, according to sources.
The 27-year-old Bennett had a career-high nine sacks last season for the Buccaneers, starting all 16 games for the first time in his career.
Originally signed as an undrafted free agent, Bennett has 15 sacks in 50 career games (28 starts).
Bennett dealt with shoulder pain last year, according to a league source, but still played in all 16 of Tampa Bay's games.