The extent of Johnathan Thurston's knee injury will be discovered today but it is hoped he will be fit for the finals.

Thurston suffered the injury as he attempted to tackle NSW forward Anthony Watmough in last night's State of Origin decider and had to be stretched off the field.

Queensland coach Mal Meninga gave hope to Cowboys fans saying he thinks it may be a grade two medial tear which has a four-to eight week recovery period, and not as serious an injury as immediately thought.

Thurston is likely to miss the remainder of the season however.