McLean, 29, will need three months of rehab after damaging medial ligaments against Barnsley on Saturday – in what was Norwich’s last game of the season.
“Kenny McLean is set to be out of action for a period of 12 weeks following confirmation of a knee ligament injury,” the Championship club said on their official website.
“Subsequent scans and further assessments have since revealed significant damage to the medial collateral ligament in McLean’s right knee.
“McLean will now undergo further assessment with an orthopaedic consultant to ascertain a management and rehabilitation plan for the injury.”
The former St Mirren and Aberdeen midfielder was forced out of Norwich’s 2-2 draw at Barnsley early in the second half after being denied by a sliding challenge in the penalty box.
He reappeared on the Oakwell pitch wearing a knee brace and using crutches as he and his team-mates collected the Championship trophy.
McLean made his senior debut for Scotland against the Czech Republic in March 2016 and has made a total of 20 appearances, scoring one goal.
He featured in all three of Scotland’s World Cup qualifiers in March, starting in the 4-0 win against the Faroe Islands at Hampden Park.
Scotland begin their Euro 2020 campaign against the Czech Republic on 14 June.
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