Reports have emerged from the Cobham training ground of last season's Premier League runners-up that the Ghanaian has damaged cruciate ligaments on the first day of full training.
Essien has been troubled by knee injuries in the past and it has been suggested that the problems have decreased his impact as a player.
The 28-year-old was unavailable for a large chunk of the 2008/09 season due to cruciate knee ligament damage.
Essien then suffered a medial ligament injury at the African Nations Cup last year and missed the 2010 World Cup as a consequence.
