The England Under-21 international, who was effectively ruled out for the rest of the season with anterior cruciate ligament damage in December last year, may now face a further spell on the sidelines.
He is due to see a specialist this week to discover whether or not further surgery is required.
Manager David Moyes said: "Duncan Watmore might be needing a little bit of work done on his knee
Obviously, he's not back, but he might be needing a little bit more surgery on his knee.
"He's been feeling it - he's been running a little bit - so he'll see the surgeon this week."
Watmore, 23, has been one of the few bright sparks for the Black Cats this season as they attempt to stave off relegation for the fifth successive year.
His pace and direct approach have been badly missed as Sunderland have struggled to provide support to leading scorer Jermain Defoe in recent months.
Source : PA
Source: PA