The Boston Celtics are currently riding the wave of a six-game winning streak, but it sounds like they'll be without the services of Al Horford for a few games due to a knee injury.

According to a report from ESPN, Horford has been diagnosed with patellofemoral pain syndrome in his left knee, which is a condition in which the cartilage under the kneecap is damaged due to injury or overuse.

“This is one of those things that it just wasn't getting better,” Horford said, according to the Celtics' official Twitter account.

Earlier this week, Horford noted that he's been dealing with knee inflammation for nearly a month.

“I don't want to have to keep dealing with this and have a question mark game after game,” Horford told reporters on Tuesday. “I just have to listen to the training staff and what the doctors are telling me. I've got to buy into that.”

Horford has become an integral piece of Boston's front-court rotation. In his 22 games played this season (all starts), the former No. 3 overall pick has racked up averages of 12.4 points on 49.1 percent shooting from the field (34.1 percent from beyond the arc), 6.4 rebounds, 3.4 assists, 1.7 blocks and just under one steal (0.8) in 30.0 minutes per outing.

Though they continue to rattle off wins, the Celtics have been dealing with several injuries through the early stages of this season. Horford is now out, and Aron Baynes (ankle) is listed as questionable for Wednesday night's game against the Wizards. If Baynes can't play in Wednesday's match-up, Daniel Theis, who started against the Pelicans on Monday night, will likely see an up-tick in his usage rate.

Wednesday's Celtics-Wizards game is scheduled to tip inside Capital One Arena at 7:00 p.m. EST.