Lyric discussion by PunkD 

Cover art for The Knot lyrics by Most Precious Blood

I think end of the song sums it all:

The knot became the noose

You tie a knot between you and the other person you are close to - meaning, you're together (in any way - love or friendship). If things go sour between you and that person, the knot actually becomes the noose (as in, killing you). That's what this song's about - a person you were once close is now against you.