Marcin Gortat provided 16 points and 17 rebounds for Washington, which trailed 52-49 at halftime but came back for its third win in four games.
Martell Webster contributed 19 points and Bradley Beal added 18.
Wall also recorded seven assists.
Carmelo Anthony accounted for 23 points and 12 boards for the Knicks, but it wasn't enough to prevent their sixth loss in eight contests.
J.R. Smith came off the bench to score 15 points.