Bolton decided to send O'Brien to leading knee specialist Dr Richard Steadman to try and clear up the problem and the club are hopeful the Republic of Ireland international will return to action before the end of the season.
Trotters assistant manager Chris Evans declared the surgery a success.
"Everything went well. Richard Steadman is the leading specialist in his field and Joey has known him previously," said Evans.
"The doctor was pleased with what he saw and the diagnosis was far better than had been feared.
"We wanted him to have the best treatment available, so we sent Joey with a member of our medical staff right away.
"The diagnosis was swift and favourable. We think that he could be back in about eight weeks, if everything goes according to plan.
"It will be nice to have him back available after a long time out on the sidelines."
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