Defender suffered the problem during Manchester United match
Chelsea have confirmed that defender Kurt Zouma has been ruled out for the rest of the season.
The player has been told that he will have to undergo surgery on his injured anterior cruciate, which he suffered in an awkward landing during yesterday's 1-1 draw against Man United.
Chelsea say that they expect the player to be out for up to six months.
In a statement, they said: "Chelsea Football Club's medical team have diagnosed that Kurt Zouma sustained an injury to his anterior cruciate ligament during yesterday’s (Sunday) Premier League game against Manchester United.
"Kurt will undergo surgery in the next 48 hours and is expected to be out for approximately six months."
It also means that the 21-year-old, who has two France caps to his name, is ruled out of Euro 2016 on home soil this summer.