Songfacts®:

• This track finds Foo Fighters leader Dave Grohl returning to his Nirvana-era roots with Nevermind producer Butch Vig at the helm and Nirvana bassist Krist Novoselic making a guest appearance. Grohl told Q magazine that he has always stayed in touch with Novoselic and called him in when he felt the song would benefit from his former bandmate's bass and accordion skills. "One of the things about the expanded Nirvana family, it doesn't matter how much time has passed, when you see each other you're immediately connected by that, by the good and bad things," he explained. "When I see Krist, I hug him to celebrate our lives, but I also hug him to console him. There's a song called 'I Should Have Known' that I thought would sound great with his bass-playing and accordion-playing. It's probably the darkest song on the album."
• Butch Vig told MTV News about finding himself in the same room as Grohl and his former Nirvana mate Krist Novoselic and watching the pair exorcise old demons on this track. "We had Krist Novoselic come in and play bass [on the song], and I'm not exactly sure what the song's about, but to me, it seems there's definitely some references about Kurt Cobain, and it's one of the most primal, raw things the Foo Fighters have ever done, and I think it's one of the best tracks on the record," he said. "It's distorted and raw, and Dave, the take on the vocals is like the first take he did at the end of the song. He's just blowing his lungs out. We played the record for some people yesterday, and the whole record is great, but that song, God, it's quite an emotional roller-coaster ride when you hear it."
• Lyrically, the song examines the conflicting emotions felt by Grohl following the loss of his childhood friend Jimmy Swanson to a drug overdose in 2008. The frontman also sung about his buddy's needless death on the 2008 track, "Word Forward."
• A portion of this power ballad was used in the Foo Fighter's Back and Forth career documentary movie to accompany the tale of Kurt Cobain's tragic demise.