Hi Psygorn,

I use http://hypatiastudio.com/celticknots/ website before rework models with MoI.
This site is very nice and you can do many sort of knots but you can't do all you could expect.

This site permits to export STL files.
I translate STL to OBJ before an import OBJ in MoI. For this I use the Max's version because MoI's OBJ import does a subd and does a combining of faces which break my remodeling process.

You could use this knot "as is", but it's a facecetted version.
I prefer to remodel the knot by doing it with a sweep operation.
I have to build a path from the OBJ import.

The process isn't very hard, but not very fast.
In Hypatia website, I use a hexagonal base.
This base gives a front edge and a back edge.
The path, I want is the middle between those 2 edges.
To extract easily the 2 edges (front and back), I use a script (you could find it on forum) to extract "continuous" edges (parametrable because it select the edges which are close to an angle between the edges).
I rebuild (ReconstructCurve) the front and back edges to create soft curves.
A loft between the 2 curves created give me a surface and I extract the middle of this with a "Curves / Iso" operation.
It gives me the path of the knot.

With a circle and the path, the sweep gives a knot.
exemple before/after at http://moi3d.com/forum/index.php?webtag=MOI&msg=10262.6