Ramis, a summer signing from Real Mallorca, was taken off on a stretcher during the 1-1 draw with Fulham at the weekend.
He has ruptured his anterior cruciate ligament in his right knee and will now be absent for the remainder of the campaign as Wigan aim to avoid relegation.
However, Wigan manager Roberto Martinez believes the injury could have been even worse.
Martinez told the club’s official website: "Nothing can disguise the fact this is a massive blow because Ivan is a key member of the group but we are relieved that the injury is not as severe as we feared it could have been.
"The most important thing now is to think of Ivan's welfare, get the operation completed, and for him to begin his rehabilitation. Ivan is a very strong and positive character and he is determined to return to fitness as soon as he can.
"He will receive the best possible medical rehabilitation as the club ensures to have him return as an even stronger footballer."
Wigan do have another alternative in Roman Golobart, but the 20-year-old's relative lack of experience means Martinez may be forced to use Emmerson Boyce as an orthodox defender, rather than in the wing-back role where he has excelled over the past 12 months.