Kind of a weirdly specific thing to ask about, but I guess it's one of those hallmarks of the subgenre. If you read a lot of omegaverse or shifter romance, the knotting comes up constantly—it's basically this physical locking mechanism during mating that ensures, well, pregnancy. Authors usually get pretty anatomical about it, describing the swelling at the base of the werewolf's... uh, anatomy, and the subsequent stretch and fullness for the omega or human partner.
You get a whole range of tones. Some writers lean into the clinical, almost biological necessity of it for world-building, especially in fated mate stories where it's part of the 'claim'. Others go full-on steamy, focusing entirely on the sensation—overwhelming, inescapable, intensely intimate, that sort of thing. I've seen it used as a plot device for forced proximity, too, like they're literally stuck together until it goes down, which can lead to some awkward or surprisingly tender conversation scenes.
What gets me is how the description changes with the story's mood. In a darker romance, it might be framed as possessive or a bit terrifying. In a fluffier one, it's all about the bonding and comfort. The words 'swell', 'lock', 'tie', 'knot' itself—they're repeated like a mantra. After a while, you just skim those paragraphs because you know exactly what's coming.