The 29-year-old swimmer tore his MCL and sprained his ACL when an overly excited teenager girl ran into him Sunday in Florida.
"As a result of a freak injury caused by an unexpected fan encounter, Ryan has suffered a torn MCL and an ACL sprain and will be taking a break from training and competition," Lochte's rep said in a statement.
"His medical team expects him to make a full and speedy recovery, and Ryan thanks everyone for their well wishes."
TMZ said that Lochte smashed his knee on the curb when the girl toppled him to the ground.
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