Manchester City have revealed that Gabriel Jesus "suffered a medial collateral ligament injury" during Sunday's goalless draw with Crystal Palace in the Premier League.
Jesus was forced off the field in the 23rd minute of the match after falling awkwardly.
The 20-year-old had to be consoled on the touchline as he feared serious damage had occurred, and medical tests have revealed the extent of the problem.
"Manchester City can confirm Gabriel Jesus suffered a medial collateral ligament injury during the 0-0 draw with Crystal Palace on Sunday," read a statement on City's official website.
"He will undergo further examinations in the coming days to establish the extent of his layoff. We wish Gabriel a speedy recovery and we will keep you updated on his progress via the club's official channels."
There is currently no timeframe on when Jesus, who has scored 10 times in 27 matches for City this season, will return to action.