The former Aberdeen midfielder suffered a meniscus tear during Saturday's win at Middlesbrough and now faces an anxious wait for scan results to determine the severity of the injury, and whether it requires surgery.
The 28-year-old scored the crucial fifth penalty in both shoot-out wins over Israel and Serbia that booked Scotland's place in next summer's Euros and will not want an extended absence to jeopardize his chances of making Steve Clarke’s squad for the finals.
Norwich manager Daniel Farke said: "We scanned him this morning after he twisted his knee and he has a meniscus tear.
"We will wait for the injury to settle down and he will see a specialist this week. We will also handle this in a conservative way.
"He will be out for six weeks or if he needs surgery it could be four to five months."