The 24-year-old, who picked up the injury against Leeds United in the middle of the month, is expected to undergo an operation this week.
He told the club's official website: "I know the rehab and what I need to do to get back to full fitness. It's going to be a long journey, but one I'm willing to throw myself at.
"The main thing is mentally getting your head around it. It's gutting, it's frustrating - every day of my life is football. I'm missing it already. But I've come back from an injury before.
"The medical staff are brilliant, they'll keep my spirits up and make sure I do all my rehab. Hopefully I can be back sooner than expected."
Karacan has been with Reading since 2003.