Allen was first placed on the injury list with a shoulder problem Nov. 9, but he played through the pain. Allen said he didn't know when his labrum was torn.
"It's not good," Allen said. "My inside game wasn't as good as I would have liked for it to have been just because I really didn't have as much power in my hump. ... But you fight through it and you're never fully healthy. I'll get it cleaned up.
"This is the first time I'm every going underneath the knife. I had my tonsils out when I was 5, but that's it."
Allen had just 12 sacks in 2012 after he posted 22 in 2011. This was just the second time in six seasons that Allen was held to less than 14.5 sacks.
Credit goes to the five-time Pro Bowl pick for being able to play with a shoulder tear at a position that requires constant hand-fighting and arm strength at the point of attack.