It was the seventh double-double in eight games for Monroe, whose elbow was partially responsible for Knight's injury.
"That's mostly just effort," Monroe said. "I know this is our seventh game in nine nights, but we just have to keep working hard. That's how this whole season is going to be."
Russell, whose father played for the Pistons in the 1980s, came off the bench to add nine points and four assists.
"I've been playing more in the last few games, and that helped me a lot tonight," said Russell, who played a career-high 33 minutes. "Coming off the bench like this is new for me, but getting more time has gotten me in sync with my teammates, so I was comfortable running things."
Rodney Stuckey added 17 for Detroit (6-20), which won consecutive games for the second time this season and had five scorers in double figures.
"Walker really held down the fort when we lost Brandon," Pistons coach Lawrence Frank said. "Brandon was begging to go back into the game, which shows you what kind of heart he has, but that wasn't going to happen. He'll get it set tomorrow, get fitted for a mask on Monday and we hope to have him back on the floor for Tuesday's practice."
New Orleans (4-20) lost its fifth straight. Trevor Ariza led the Hornets with 26.
Both teams spent most of the game without their starting point guards. New Orleans' Jarrett Jack missed the game with a knee injury, and Knight was lost early.
The Hornets led 44-41 at the half, but Monroe helped the Pistons take a 65-61 lead into the fourth quarter.
"This is the dog days of the NBA right now," New Orleans coach Monty Williams said. "A lot of players are kind of going through the motions right now, and we certainly played that way tonight. I thought we'd be fresher because I gave them yesterday off, but maybe that hurt us."
By that point, Carl Landry had left the game with a left knee injury, and the Pistons took advantage. Four straight points from Stuckey gave Detroit a 75-65 lead with 7:50 to play.
Greivis Vasquez, though, scored the first seven points in a 9-0 New Orleans run that pulled the Hornets to within a point with 5:22 to play. That was as close as the Hornets got, however. Monroe scored the next basket on an offensive putback, and Stuckey's jumper put Detroit up 83-76 with 1:45 left.
"Give them credit, they played harder at the end of the game," Vasquez said. "I think that's the biggest weakness of this team, breaking down when we are in tough times. We had big turnovers and they beat us on the offensive glass."
Knight joined a Detroit injury list that already included Will Bynum (foot strain), Ben Gordon (shoulder) and Charlie Villanueva (ankle). Bynum and Gordon both hope to return to practice on Monday, while Villanueva is expected to miss most of the season. ... Chris Kaman, who was sent home by the Hornets while they tried to trade him, is expected to rejoin the team in the next two days. ... Jason Smith left the game in the fourth quarter after being floored by two separate shots to the head in the second half.