The club can confirm that Jake Forster-Caskey suffered an ACL injury during Tuesday’s game against Lincoln City.
As a result the 27-year-old midfielder will miss the remainder of the 2020/21 season.
Charlton Manager Nigel Adkins said: “Jake has had a fantastic season and has been a really important part of our team. He has begun rehabilitation and will be provided with excellent medical care and attention throughout his recovery.”
Forster-Caskey said: "It’s a tough blow to take. But a bump in the road does not end the journey. My focus now is to get back and be more influential than ever. The support of the fans means everything."