No timetable was given for Johnson's return.
Johnson suffered the injury Friday in the first quarter of the Suns' 108-106 loss to the Trail Blazers when he landed awkwardly while trying to plant his foot and run in the other direction.
He immediately started limping and came out of the game shortly afterward.
Johnson has been a key contributor over the past few years and moved into a starting role this season. He's averaging a career-high 13.0 points and scored a season-best 29 points Tuesday in a win over the Timberwolves.
Johnson is in the final year of his rookie contract after failing to sign a long-term extension before the season. The Suns' ownership situation is in flux after Robert Sarver announced he would explore selling the team following his one-year suspension by the NBA over workplace misconduct that included racist speech and hostile behavior toward employees.
Information from The Associated Press was used in this report.