  We report on an angular resolved X-ray Absorption Spectroscopy study of
$La_{0.7}Sr_{0.3}MnO_{3}$ thin films epitaxially grown by pulsed laser
deposition on slightly mismatched substrates which induce tensile or
compressive strains. XANES spectra give evidence of tetragonal distortion
within the $MnO_{6}$ octahedra, with opposite directions for tensile and
compressive strains. Quantitative analysis has been done and a model of
tetragonal distortion reflecting the strain has been established. EXAFS data
collected in plane for tensile substrate confirm the change in the $Mn-O$
average bond distance and the increase of $Mn-Mn$ length matching with the
enlargement of the cell parameter. From these results we conclude that there is
no significant change in the $Mn-O-Mn$ angle. Our observations conflict with
the scenarios which this angle is the main driving parameter in the sensitivity
of manganite films properties to external strains and suggest that the
distortion within the octahedra plays a key role in the modification of the
transport and magnetic properties.
