Howard missed training camp, preseason and the team's first seven games due to a strained muscle in his lower back near his tailbone.
Meanwhile, the Wizards (1-6) missed both his rebounding and defense. Washington is getting outrebounded by 12.1 boards per game and are allowing a league-worst 122.4 points per game. The team is allowing opponents over 13 offensive rebounds per game.
"Well, we're being outrebounded quite a bit," coach Scott Brooks told the Washington Post. "And historically, (Howard's) been one of the best rebounders year-in, year-out as a 15-year veteran in this league. ... So, rebounding is definitely something that we have not done a very good job (of). In that regard, he brings that. He brings a sense of importance of rebounding the basketball to our ballclub. We need it."
The 33-year-old Howard, who signed with Washington as a free agent in the offseason, averaged 12.5 rebounds per game last season and should make an immediate impact even though he's still recovering and feels pain when he's sitting down.
"It just doesn't go away. It's a lot better than it was," he told NBCSportsWashington.com. "I haven't even been able to sit down. It hurts to sit down. Every time I get home, I can't watch a movie sitting down. I've gotta lay down on the floor. It's very painful."
Brooks didn't say how much Howard will play against the Thunder, but even a hurting Howard should improve Washington, which has lost four straight games.
"I'm just looking forward to doing what I can to help this team win," Howard told reporters.
The Thunder (3-4) come into Washington winners of three straight. Russell Westbrook had 29 points, 10 assists and eight rebounds, and Oklahoma City rallied to beat the Hornets 111-107 on Thursday night in Charlotte.
Oklahoma City overcame a 19-point third-quarter deficit.
Alex Abrines had a career-high 25 points on five 3-pointers for the Thunder and Dennis Schroder added 21 points.
"He's a shooter, man," Westbrook told the Daily Oklahoman about Abrines. "He knows how to play the game of basketball, and he's improved himself from last year. You saw it tonight."
Westbrook struggled for three quarters and Paul George (11 points on 4-of-20 shooting) struggled on offense the whole night but grabbed 10 rebounds. Westbrook hit 12 of 24 shots from the field and scored 13 of his points in the fourth quarter. He shot 6-of-7 in the fourth, including 3-of-4 outside the paint.
"I'm fortunate I play with one of the baddest (expletive) in this league," George told the Oklahoman. "Excuse my language, but it's the best way to describe him. Just straight toughest dude out there."
George told reporters after the game that he's been dealing with a peroneal nerve palsy or "dead foot" and that he's planning to play through it.
The Thunder lead the NBA in free throws attempted per game and made 21 of 29 Thursday night.