SAN FRANCISCO -- Jon Kitna sprained his right knee in the final minutes of Detroit's 31-13 loss to San Francisco on Sunday, and the Lions didn't know how long their veteran quarterback would be sidelined.
Kitna, who went 15-of-30 for 146 yards, was hurt while getting pulled down on a sack by 49ers linebacker Parys Haralson with 1:50 left in the fourth quarter. The 12th-year pro hobbled to the bench, where the team's medical staff surrounded him on a rough end to his 36th birthday.
"It feels pretty bad right now," said Kitna, who threw one TD pass and one interception. "I just got beat up all day. The play at the end was a culmination of four or five hits. The first one was in the first quarter. ... I just came down on my knee. Sometimes when you have a bruise or something's there, and then it happens again, the pain is excruciating at first."
Dan Orlovsky replaced Kitna, but his only throw was immediately intercepted by defensive lineman Justin Smith, who hadn't picked off a pass since his rookie season with the Cincinnati Bengals in 2001.
Smith also sacked Kitna for a 12-yard loss in the first half, forcing a fumble that was recovered by center Dominic Raiola at the Detroit 2. Kitna has been sacked 12 times in three games this season after absorbing an NFL-high 51 sacks last year.
The Lions are off next week after their fourth 0-3 start in eight years. Coach Rod Marinelli wouldn't speculate on how long Kitna might be sidelined until the team's medical staff did more evaluation back in Michigan.
Orlovsky has thrown five passes in two games this season after spending the two previous years on the sideline as Detroit's No. 3 quarterback. He played in two games during his rookie season in 2005, but has never started an NFL game.
Detroit's third-stringer, Drew Stanton, spent last season on injured reserve as a rookie from Michigan State.
Kitna was downcast after the game, acknowledging disappointment in both his injury and the Lions' 67-yard performance in the first half. Detroit has just 859 net yards in its first three games while getting outscored 113-59.
"We're not consistent enough to win football games, but hopefully we will be soon," Kitna said. "I couldn't seem to get into a good rhythm today."