Gronkowski raised his right arm to the crowd as he left on a cart in the third quarter.
He was hurt on a hit by Browns safety T.J. Ward after a reception from Tom Brady with the Browns leading 12-0. Ward was among many players from both teams who went up to Gronkowski before he left the field.
Gronkowski missed the first six games after offseason surgeries on his broken left forearm and back. In six games before Sunday, he led NFL tight ends with 37 catches and 560 yards receiving. He had two catches for 32 yards Sunday.