Gagne, the 2003 NL Cy Young Award winner, missed the first 35 games of the season with a similar injury.
"It's the same situation he was dealing with in spring training," said Dodgers Manager Jim Tracy. "He said he felt burning there."
Gagne set a major-league record of 84 consecutive converted save opportunities over 2003-04. He is one of three pitchers in major league history to record 45 or more saves in three seasons.
Yhency Brazoban, who filled in for Gagne with 11 saves at the start of the season, will again assume the main closer's role for the Dodgers.