  Twisted knot theory, introduced by M.O.Bourgoin, is a generalization of
virtual knot theory. It is easily shown that any virtual knot can be deformed
into a trivial knot by a finite sequence of generalized Reidemeister moves and
two "forbidden moves" $F_{1}$ and $F_{2}$. Similarly, we show that any twisted
knot also can be deformed into a trivial knot or a trivial knot with a bar by a
finite sequence of extended Reidemeister moves and three "forbidden moves"
$T_{4}$, $F_{1}$ (or $F_{2}$) and $F_{3}$ (or $F_{4}$) .
