We examine the symmetry of
the complement of a non-trivial knot K in S3 and obtain a classification of the
actions of finite groups on the complement of a non-trivial knot in the case
where the actions extend to non-fixed point free actions on the three sphere.
We prove the result by showing first an extension theorem which says that
any action of finite group on a non-trivial knot complement extends to an
action on the three sphere and then by applying the solution of the Smith
conjecture.