He played college football at Illinois, and was selected by the Indianapolis Colts in the third round of the 2013 NFL draft.

Thornton has also been a member of the Atlanta Falcons, Arizona Hotshots, Washington Redskins and Calgary Stampeders.

[1] He began his rookie season as a backup to Mike McGlynn and Donald Thomas at offensive guard.

However, he was made a starter after Thomas sustained a season ending quadriceps tear in a week two loss to the Miami Dolphins, and would go on to start 12 regular season games at left guard as a rookie, in addition to the two playoff games that the Colts played in that postseason.

[9] On April 8, 2022, Thornton signed with the Calgary Stampeders of the Canadian Football League (CFL).