  The four dimensional O(3) non-linear sigma model introduced by Faddeev and
Niemi, with a Skyrme-like higher order term to stabilise static knot solutions
classified by the Hopf invariant, can be rewritten in terms of the complex
two-component CP1 variables. A further rewriting of these variables in terms of
SU(2) curvature free gauge fields is performed. This leads us to interpret
SU(2) pure gauge vacuum configurations, in a particular maximal abelian gauge,
in terms of knots with the Hopf invariant equal to the winding number of the
gauge configuration.
