The 34-year-old signal-caller revealed the news in a Twitter post and later confirmed it with the NFL Network.
"Nothing happened, just Father Time, wear and tear," Garrard told the broadcaster. "They have to take out loose things floating around."
Garrard, who didn't play last season after being released by the Jacksonville Jaguars, was expected to be part of a three-way competition with Matt Moore and Ryan Tannehill for the Dolphins' quarterback job.
In nine seasons with the Jags, Garrard went 1,406-of-2,281 through the air for 16,003 yards, 89 touchdowns and 54 interceptions.