  Testing modified theories of gravity with direct observations of the
parameters of a neutron star is not the optimal way of testing gravitational
theories. However, observing electromagnetic signals originating from the close
vicinity of the compact object my turn out an excellent way of probing
spacetime in strong field regime. A promising candidate for doing so are the
so-called quasi-periodic oscillations, observed in the X-ray light curves of
some pulsars. Although the origin of those oscillations is unknown, one thing
most of the models describing them have in common is that in one way or another
they incorporate the radius of the innermost stable circular obit, and the
orbital and the epicyclic frequencies of particles moving around the compact
object. In this paper we study the aforementioned quantities in the context of
massive scalar-tensor theory and massive scalar-tensor theory with
self-interaction, both of which in strong regime allow for significant
deviations from General relativity for values for the free parameters of the
theory in correlation with the observations.
