You could use XY-pic
I didn't really like Simon's link. It has an option for The tutorial there seems to be based solely on drawing knotsthe curves by specifying coordinates.
And I find that a more, say, tabular or rigidly based approach is much easier to work with.
There's a good xy-pic tutorial for creating knots at http://lf.starlogik.de/res/XYPic-Knot-Intro.pdf
There's a great xymatrix tutorial at http://www.ctan.org/tex-archive/macros/generic/diagrams/xypic/xy/doc/xyguide.pdf
There are only 10 pages to read in each manual and you'll have mastered them both. The You could get away without reading the xymatrix tutorialisn't really necessary, but I'd reccommend reading it because it goes more in-depth into some of the parameter modifiers that aren't actually explained in the knot manual.