A person familiar with the decision told The Associated Press on Wednesday that Gronkowski will undergo the surgery next month, which means he will miss the rest of offseason training activities with the Patriots. He could return for training camp at the end of July.
The person spoke on condition of anonymity because the Patriots do not reveal injury details publicly.
Gronkowski missed the 2009 season at the University of Arizona after back surgery. Earlier this month, he underwent a fourth procedure on his left forearm, which he broke last season, to treat an infection.
He broke the forearm Nov. 18 while blocking for an extra point against the Indianapolis Colts. He broke it again early in the Patriots' first playoff game, a win over Houston, ending a rough season for the star tight end.
Gronkowski had 55 receptions and 11 touchdowns despite missing five of the 16 regular-season games last year. The previous year, he had 90 catches for 1,327 yards and a league-high 17 touchdowns.
New England has built its offense around Tom Brady's passing to Gronkowski and fellow tight end Aaron Hernandez. With slot receiver Wes Welker gone to Denver as a free agent, the Patriots will need Gronkowski at full strength when they open the season on Sept. 8.