The 25-year-old picked up the problem during the opening minutes of Scotland's World Cup qualifier against Wales on Friday night.
The centre-forward was unable to walk off the pitch and as a result left the field of play on a stretcher.
He has now met with the Sunderland medical team and has undergone a scan, with the results due to be revealed tomorrow.
Restore Data
| Team | P | W | D | L | F | A | GD | PTS | |
| 1 | Sunderland | 9 | 6 | 1 | 2 | 18 | 8 | 10 | 19 |
| 2 | Sheffield UnitedSheff Utd | 9 | 6 | 3 | 0 | 12 | 3 | 9 | 19 |
| 3 | Burnley | 9 | 5 | 3 | 1 | 14 | 4 | 10 | 18 |
| 4 | West Bromwich AlbionWest Brom | 9 | 5 | 2 | 2 | 12 | 6 | 6 | 17 |
| 5 | Leeds UnitedLeeds | 9 | 4 | 4 | 1 | 15 | 7 | 8 | 16 |
| 6 | Watford | 9 | 5 | 1 | 3 | 14 | 14 | 0 | 16 |
| 7 | Norwich CityNorwich | 9 | 4 | 3 | 2 | 16 | 10 | 6 | 15 |
| 8 | Blackburn RoversBlackburn | 9 | 4 | 3 | 2 | 15 | 11 | 4 | 15 |
| 9 | Middlesbrough | 9 | 4 | 2 | 3 | 10 | 7 | 3 | 14 |
| 10 | Oxford UnitedOxford Utd | 9 | 3 | 3 | 3 | 13 | 11 | 2 | 12 |
| 11 | Swansea CitySwansea | 9 | 3 | 3 | 3 | 8 | 6 | 2 | 12 |
| 12 | Derby CountyDerby | 9 | 4 | 0 | 5 | 12 | 12 | 0 | 12 |
| 13 | Hull City | 9 | 3 | 3 | 3 | 12 | 13 | -1 | 12 |
| 14 | Plymouth ArgylePlymouth | 9 | 3 | 2 | 4 | 10 | 13 | -3 | 11 |
| 15 | Sheffield WednesdaySheff Weds | 9 | 3 | 2 | 4 | 11 | 15 | -4 | 11 |
| 16 | Stoke CityStoke | 9 | 3 | 1 | 5 | 10 | 12 | -2 | 10 |
| 17 | Bristol City | 8 | 2 | 4 | 2 | 9 | 13 | -4 | 10 |
| 18 | Millwall | 9 | 2 | 3 | 4 | 12 | 11 | 1 | 9 |
| 19 | Preston North EndPreston | 9 | 2 | 3 | 4 | 7 | 12 | -5 | 9 |
| 20 | Coventry CityCoventry | 9 | 2 | 2 | 5 | 10 | 13 | -3 | 8 |
| 21 | Luton TownLuton | 9 | 2 | 2 | 5 | 8 | 15 | -7 | 8 |
| 22 | Queens Park RangersQPR | 9 | 1 | 4 | 4 | 9 | 16 | -7 | 7 |
| 23 | Portsmouth | 9 | 0 | 5 | 4 | 9 | 20 | -11 | 5 |
| 24 | Cardiff CityCardiff | 8 | 1 | 1 | 6 | 3 | 17 | -14 | 4 |
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