The Heat announced that Johnson will be in a cast for six weeks but that he is expected to be fully recovered and available for training camp later this year.
Johnson suffered the injury in Game 3 of Miami's first-round playoff series against the Philadelphia 76ers. He played the rest of the series despite the injury and scored 16 points in Miami's season-ending loss in Game 5.
Johnson, 25, averaged 11.7 points and 3.4 rebounds in 72 games this season. He is entering the third year of a four-year, $50 million deal and will make more than $19 million in 2018-19.