  We report muon spin rotation measurements of the local magnetic
susceptibility around a positive muon in the paramagnetic state of the quasi
one-dimensional spin 1/2 antiferromagnet KCuF$_3$. Signals from two distinct
sites are resolved which have a temperature dependent frequency shift which is
different than the magnetic susceptibility. This difference is attributed to a
muon induced perturbation of the spin 1/2 chain.
