Songfacts®:

• "Knock You Down" features Kanye West and Ne-Yo, who also appear as Keri Hilson's two love interests in the music video. The song finds all three of them bouncing back from romantic disaster to find a love that has them hooked for good. It's not clear if we're dealing with a love triangle here, but West does say, "You should leave your boyfriend now" at the end of his last verse.
  
  The song was a big hit, going to #3 on the Hot 100 and topping the R&B chart. All three artists were red hot: Kanye West had recently released his 808s & Heartbreak album with the hits "Love Lockdown" and "Heartless"; Ne-Yo was coming off his album Year Of The Gentleman, which includes his hit "Miss Independent," which he namechecks in his verse ("Miss independent to the fullest, the load never too much"). The song is part of Hilson's debut album, In a Perfect World..., but she had featured on the Timbaland hit "The Way I Are" in 2007 and had some impressive writing credits, including "Gimme More" by Britney Spears.
• Ne-Yo made his contribution to the song first. Kanye West then met up with Hilson after the album had been recorded and was given an exclusive preview to see on which song he'd like to feature on. He chose "Knock You Down" even though Ne-Yo was already on the track.
• Keri Hilson made her mark in the Atlanta music scene and teamed with two hitmaking producers, Timbaland and Polow Da Don, to make her In a Perfect World... album.
  
  "Knock You Down" started off as a track written by Timbaland collaborator Danja Hills and lyricist Kevin "KC" Cossom, whose previous credits include Rick Ross' "Speedin'," Akon's "One" and T-Pain's "Cash Flow." Cossom told MTV news that producer Hills sent the vocals to Polow Da Don thinking it would be right for a male singer, but Polow thought the song was perfect for Hilson.
  
  Cossom recalled: "I didn't hear anything about the record for a couple of months, and Danja came and was like, 'Keri cut the record,' I was like, 'OK, all right.' I wanted to hear it. By the time I got a chance to hear it, Ne-Yo had gotten on it. I felt it could be a major record. After that, Kanye jumped on it. It wasn't in the plan; it just happened. I don't think anybody imagined that would happen. I got my first #1 record - #1 Urban, #3 Hot 100."
• Kanye West got a Michael Jackson reference in with the lines:
  
  This is bad, real bad, Michael Jackson
  Now I'm mad, real mad, Joe Jackson
  
  Bad is the name of Michael's landmark 1987 album; his dad Joe was known to have a temper.
  
  The song appeared on the In a Perfect World… album March 24, 2009 and peaked at #3 on June 20. Michael Jackson died just five days later.
• This was the third hit record where Kanye West slipped in a reference to Michael Jackson. On "Slow Jamz" by Twista featuring West and Jamie Foxx, he delivers these lines:
  
  She got a light-skinned friend, look like Michael Jackson
  Got a dark-skinned friend, look like Michael Jackson
  
  And on his solo single "Gold Digger," there's:
  
  She walking around looking like Michael with your money
• Kanye West's contribution was very much a last-minute job. He laid down his rhymes the same day the In a Perfect World... album was being mastered in Canada. Hilson recalled to RatedRnB that Ye rattled off 60 bars of verse and they had to cut down to 20 bars. "It was long as hell and there was a lot a drama because we had to shorten his verse," she said.
• This song is a great example of the clever, joyful jams that were floating around in 2009. Kanye West and Ne-Yo have a lot of fun on the track, with Ne-Yo giving us this bon mot:
  
  I used to be commander-in-chief
  On my pimp ship, flyin' high
  
  Ne-Yo stayed hot for a few more years but then dropped off the charts. Hilson did too, but she bowed out of the industry to deal with mental health issues. She later revealed that her depression got so bad, she would cry on stage. She was haunted by an unofficially released remix of her 2008 single "Turnin' Me On" where she inexplicably takes a shot at Beyoncé:
  
  You can dance, she can sing
  But she need to move it to the left, left
  
  When Hilson returned with another album in 2025 she explained that Polow Da Don pressured her to record that part, which she didn't write.