"Jason Jones will be out for the season," Lions coach Jim Schwartz said. "He ruptured his patellar tendon."
Jones injured his left knee in the second quarter of Detroit's 27-20 victory Sunday over the Washington Redskins.
Jones initially tried to walk to the sidelines but eventually had to have the cart brought out to take him off the field.
Jones had signed with the Lions in the offseason from Seattle and had a history of knee issues over the past few seasons. Jones has 123 career tackles and 18.5 sacks, although he only had one tackle and one pass defended in his first two games this season.
Willie Young, who had started at the other defensive end for Ziggy Ansah in the first game of the season, will likely take over for Jones.