The Washington Redskins have signed former Cincinnati defensive end Jason Buck to replace injured defensive lineman Markus Koch.

Buck, the Bengals' first-round draft choice in 1987 from Brigham Young University, was cut by Cincinnati in training camp. He will report to the Redskins today.Koch, who was injured during Sunday's 20-7 victory over the Chicago Bears, is expected to be out at least six weeks. Trainer Bubba Tyer said the 6-foot-5, 265-pound lineman suffered a partial tear of a ligament in his left knee.

Koch played college football at Boise State University and Buck played two years at Idaho's Ricks College before transferring to BYU.

Buck played five years in Cincinnati. He worked out last week for Redskin coaches, who have been concerned about the team's lack of depth on the defensive line.

But how much Buck will play remains in question.

After Koch's departure Sunday, linebackers Ravin Caldwell and Wilber Marshall occasionally lined up in the down position when regular ends Charles Mann and Fred Stokes were on the sidelines.

And Coach Joe Gibbs said he was likely to use Caldwell in that capacity in future contests.

Gibbs said that backup defensive tackle James "Jumpy" Geathers could be shifted to end, a position he played in college, if the need arises.

Team officials said the 6-foot-5, 264-pound Buck was signed instead of 10-year Redskin veteran Darryl Grant because he has more experience playing end.

He is also taller than Grant, who is 6-foot-1 and 275 pounds. Grant was released by the Redskins at the close of training camp.

Buck had his best year with Cincinnati in 1989, when he recorded six quarterback sacks, 39 tackles and 11 assists.