Someone made a tag called "inaccurate knotting" which applies to when the knot is inserted after it inflates. In normal canine anatomy the entire penis is inserted before the knot swells inside, locking the two together.
I think it would make an interesting tag for knot fetishists. My character's knot just inflates right before orgasm.
Only furries, ones to go into immaculate detail about anatomy and then throw it out the window.