"It's just one of a dozen things [Lewis] has had that could have shut him down and didn't," general manager Jon Daniels said.
Lewis was 17-9 with a 4.66 ERA for the Rangers this season, leading the team in wins and innings pitched with 204 2/3. Manager Jeff Banister said the injury was not a factor in Lewis being left out of the playoff rotation.
"Colby had been pitching with the knee for quite a while," Banister said.
Lewis is a free agent, and the Rangers have interest in re-signing him, Daniels said.
• Catchers Chris Gimenez and Carlos Corporan also underwent surgery on Friday. Gimenez had a cleanup on his right shoulder capsule, and Corporan had surgery on his left thumb. The latter did not play in the second half of the season.
• Daniels said the Rangers have had casual conversations with first baseman Mike Napoli about re-signing for 2016. Napoli is a free agent, and the Rangers are going into the offseason looking for more right-handed hitting.
• Daniels said infielder Jurickson Profar will play in the Arizona Fall League, but only as a designated hitter. Profar has missed two full seasons because of a torn muscle in his right shoulder.
• Daniels said infielder Joey Gallo will need "more development time" next season. Gallo played in 36 games for the Rangers this season, hitting .204 with six home runs and 14 RBIs. The Rangers see him starting 2016 at Triple-A.
T.R. Sullivan is a reporter for MLB.com. Read his blog, Postcards from Elysian Fields, follow him on Twitter @Sullivan_Ranger and listen to his podcast. This story was not subject to the approval of Major League Baseball or its clubs.