  The influence of the chiral mean field on the collective motion of kaons in
relativistic heavy ion reactions at SIS energies is investigated. We consider
three types of collective motion, i.e. the transverse flow, the out-of-plane
flow (squeeze-out) and the radial flow. The kaon dynamics is thereby described
with a relativistic mean field as it originates form chiral lagrangiens. For
the $K$ mesons inside the nuclear medium we adopt a covariant quasi-particle
picture including scalar and vector fields and compare this to a treatment with
a static potential like force. The comparison to the available data ($K^+$)
measured by FOPI and KaoS strongly favor the existence of an in-medium
potential. However, using full covariant dynamics makes it more difficult to
describe the data which might indicate that the mean field level is not
sufficient for a reliable description of the kaon dynamics.
