
The 27-year-old Belgium international had joined City’s squad last week after helping his country progress to the World Cup semifinals in Russia.
He came off the bench on Sunday in City’s 2-0 victory over Arsenal in their opening Premier League match.
“Kevin De Bruyne is undergoing tests on his right knee after sustaining an injury at training on Wednesday,” the club said in a statement. “The extent of the problem is not yet known.”
In 2016, De Bruyne missed 12 games after injuring his right knee during a League Cup semifinal victory over Everton.
De Bruyne scored eight goals and made 16 assists as City lifted the league title with a record-breaking 100 points last season.