O'Neal, 32, chose not to get surgery.
"We had a discussion at halftime, Jermaine, and myself, and our medical staff, and have decided that we are not doing surgery," Celtics General Manager Danny Ainge said after the Celtics' win over Detroit Wednesday.
O'Neal has played in only 17 games this season because of the injury.
He is coming off a 70-game season with the Heat, where he averaged 13.6 points and 6.9 rebounds per game. quarterback selected for the Pro Bowl, in 2005.