Johnson was hurt while playing for Aris in a Greek league playoff game against AEK Athens on Wednesday, a day after he was selected for the 30-man preliminary U.S. roster.
He will report to training camp for the start of practice Monday, U.S. Soccer Federation spokesman Michael Kammarman said Friday.
The 26-year-old from Palm Coast, Fla., has 12 goals in 40 international appearances. He is on loan to Aris from Fulham.
World Cup teams must cut to the 23-man limit by June 1.