Stafford's injury appears the more serious of the two.
ESPN's Chris Mortensen is reporting that the Lions quarterback suffered a dislocation of his right knee. The knee popped right back into place, but he will undergo further tests when the team returns home to Detroit to see if he suffered any damage to the cartilage around his knee cap.
Sources on the team told Mortensen that Stafford could be back on the field next week, possibly with a brace, depending on how the test results turn out.
Johnson left the game in the fourth as well because of tightness in his legs, but the problem doesn't appear to be serious.
Source: http://sports.espn.go.com/nfl/news/story?id=4531166
