The Belgium playmaker came off worst in a challenge with N'Golo Kante just two minutes into the second-half and hobbled off to be replaced by Phil Foden.
City reached the last four of the Champions League for the first time in five seasons under Pep Guardiola with victory over Borussia Dortmund on Wednesday.
However, the loss of De Bruyne would be a huge blow to City's hopes of winning European football's premier club competition for the first time.
PSG host the runaway Premier League leaders on April 28 with the return leg at the Etihad Stadium just six days later.
Standout matches today