Fairley sustained the injury while rushing Falcons quarterback Matt Ryan with about 11 minutes left in the second quarter. After Ryan released the ball, Fairley collided with fellow defensive tackle Ndamukong Suh and his right leg appeared to buckle. He was helped off the field by medical personnel and later was carted off with a wrap around his knee.
The exact nature of Fairley's injury isn't yet known.
Fairley, 26, is in his fourth year with the Lions after the team selected him in the first round of the 2011 NFL draft. He has 14 tackles and one sack this season.
The defensive tackle is in the final year of his rookie contract after the Lions declined his option for 2015 but has said he wants to stay with Detroit.
Fairley's productive season has come after a somewhat rocky period since the end of last year. He received probation and a fine in August for a 2012 DUI incident and briefly lost his spot in the starting lineup during training camp before regaining it once he lowered his weight.
Along with Suh, Fairley's platy in the middle of the defensive line has helped the Lions become the No. 1 defense in the NFL this season, allowing 290.3 total yards per game going into Sunday.
- Ben Estes