The Republic of Ireland international centre-half has missed the last seven matches with the problem he sustained during the 2-0 home win over Bristol City on October 6.
However, Pearson insists he will not be rushing St Ledger back into action.
He said: "It has been a frustrating for him. When he has played this season he has done exceptionally well.
"It is one of those injuries that has taken a bit longer than both he and us thought. It is important that it is 100% before he comes back in.
"I wouldn't want him to come back and then break down. He is frustrated at the minute, but is still a very positive influence around the place."