The Chicago Tribune reported on Saturday that the team has "concerns over Forte's knees."
The Bears are privately concerned arthritis could set in, leading to a chronic problem for the fifth-year back. Forte hasn't signed Chicago's $7.7 million franchise tender, and is sitting out OTAs.
Questions about Forte's durability aren't new. According to the Tribune, the wear and tear of Forte's knees drew the attention of multiple teams before the 2008 NFL Draft. The Bears were among that group, though they took the Tulane star in the second round anyway.
Forte, 26, rewarded the Bears by becoming one of the most versatile running backs in football. Last season, he finished with nearly 1,500 total yards, this despite being shut down the last four weeks after spraining his MCL in a game against the Kansas City Chiefs.