Coach Dan Quinn said Monday that Armstrong (knee) will miss the remainder of the season, Commanders writer Ben Standig reports.
Armstrong suffered the knee injury in Sunday's loss to the Cowboys after logging just four defensive snaps. The 28-year-old defensive lineman's season is over after compiling 24 tackles (16 solo), including a team-high 5.5 sacks. Washington already has several other edge defenders on injured reserve, so the team may need to look outside the organization for help at the position.