Quantum mechanical cross section calculations have been performed in order to interpret the energy dependence of absolute total cross sections for fine-structure transitions in the 4²P level of K, induced in collisions with Ar. The comparison between the experimental and theoretical data allows available interatomic potentials to be tested. The various adiabatic potential sets used in the calculations, along with a careful analysis of the polarisation in the 4²P level of K, allow the coupling mechanisms responsible for the fine-structure transitions in K(4²P)+Ar collisions to be analysed in some detail.