The 33-year-old Italian has been without a club since being released by the Black Cats at the end of last season.
Dossena told Orient's official website: "I'm happy to be here. I can show what I can do for the team, and for me it's important to continue playing."
Orient are 20th in League One after winning just one of their last eight league games.
Restore Data
| Team | P | W | D | L | F | A | GD | PTS | |
| 1 | Wrexham | 6 | 4 | 1 | 1 | 12 | 5 | 7 | 13 |
| 2 | Birmingham CityBirmingham | 5 | 4 | 1 | 0 | 11 | 6 | 5 | 13 |
| 3 | Charlton AthleticCharlton | 6 | 4 | 1 | 1 | 6 | 3 | 3 | 13 |
| 4 | Huddersfield TownHuddersfield | 5 | 4 | 0 | 1 | 10 | 3 | 7 | 12 |
| 5 | Stockport CountyStockport | 5 | 3 | 2 | 0 | 9 | 2 | 7 | 11 |
| 6 | Lincoln CityLincoln | 5 | 3 | 1 | 1 | 10 | 6 | 4 | 10 |
| 7 | Barnsley | 6 | 3 | 1 | 2 | 10 | 9 | 1 | 10 |
| 8 | Mansfield TownMansfield | 5 | 2 | 2 | 1 | 9 | 10 | -1 | 8 |
| 9 | Stevenage | 5 | 2 | 1 | 2 | 5 | 3 | 2 | 7 |
| 10 | Wycombe WanderersWycombe | 5 | 2 | 1 | 2 | 10 | 9 | 1 | 7 |
| 11 | Peterborough UnitedPeterborough | 5 | 2 | 1 | 2 | 7 | 7 | 0 | 7 |
| 12 | Reading | 5 | 2 | 1 | 2 | 5 | 5 | 0 | 7 |
| 13 | Crawley TownCrawley | 5 | 2 | 1 | 2 | 4 | 6 | -2 | 7 |
| 14 | Bristol Rovers | 6 | 2 | 1 | 3 | 4 | 8 | -4 | 7 |
| 15 | Wigan AthleticWigan | 5 | 2 | 0 | 3 | 6 | 5 | 1 | 6 |
| 16 | Exeter CityExeter | 5 | 2 | 0 | 3 | 6 | 6 | 0 | 6 |
| 17 | Rotherham UnitedRotherham | 6 | 1 | 3 | 2 | 5 | 7 | -2 | 6 |
| 18 | Northampton TownNorthampton | 5 | 1 | 2 | 2 | 5 | 6 | -1 | 5 |
| 19 | Blackpool | 5 | 1 | 2 | 2 | 9 | 12 | -3 | 5 |
| 20 | Burton Albion | 5 | 0 | 4 | 1 | 7 | 8 | -1 | 4 |
| 21 | Bolton WanderersBolton | 5 | 1 | 1 | 3 | 2 | 9 | -7 | 4 |
| 22 | Leyton Orient | 5 | 1 | 0 | 4 | 3 | 8 | -5 | 3 |
| 23 | Shrewsbury TownShrewsbury | 6 | 1 | 0 | 5 | 4 | 10 | -6 | 3 |
| 24 | Cambridge UnitedCambridge | 5 | 0 | 1 | 4 | 5 | 11 | -6 | 1 |
| > League One Full Table | |||||||||
