Speaking to CBS News' Reena Ninan, Gronkowski said he suffered "probably, like, 20 concussions" in his life and he recalls "five blackout ones" from his playing days.
Following his retirement from the NFL in March, Gronkowski elaborated on his decision in August.
"I want to be clear to my fans," he said, per ESPN.com's Mike Reiss. "I needed to recover. I was not in a good place. Football was bringing me down, and I didn't like it. I was losing that joy in life."
Gronkowski added he "could barely walk" after New England's victory over the Los Angeles Rams in Super Bowl LIII because of a quad injury he suffered during the game.
Despite all of the injuries, Gronkowski told Ninan he would allow his son—should he have one—to play football after he educated him about the game and everything he went through to play.
Gronkowski retired at age 29 after nine years with the Patriots. He missed at least one contest because of injuries in six of his final seven seasons and didn't play a full 16-game schedule after the 2011 campaign.