Knorr replaces Pat Corrales, who became Washington's bench coach when Davey Johnson took over as manager after Jim Riggleman abruptly resigned during last season.
Otherwise, the Nationals announced Thursday that Johnson's staff will stay the same in 2012: hitting coach Rick Eckstein, pitching coach Steve McCatty, third base coach Bo Porter, first base coach Trent Jewett and bullpen coach Jim Lett.
Knorr retired as a player in 2004. He is 384-380 as a manager in the minors, including at Triple-A Syracuse in 2011. He was the Nationals' bullpen coach for part of the 2006 season and all of 2009.