If we talk about the engineering properties of real knots in 3D space, then that is something entirely different from the topology of ideal knots, which has to do with enumerating the unique ways in which they loop around an intersect themselves. Those properties don't change even if the knot is left entirely loose, so that the string never touches itself.

Is it true that current mathematics cannot explain what's going on in a 3D knot in space? Even if a closed equation couldn't solve it symbolically, surely we must have have clever people who can build a finite element model of it and do it numerically.