  We show that the short-scale elastic distortions that are excited in the
vicinity of the joint between different lipidic membrane domains (at a scale of
\~10 nm) may produce a "crease" from the point of view of the standard elastic
description of membranes, i.e., an effective discontinuity in the membrane
slope at the level of Helfrich's theory. This "discontinuity" may be accounted
for by introducing a line tension with an effective angular dependence. We show
that domains bearing strong spontaneous curvatures, such as biological rafts,
should exhibit creases with a finite contact-angle, almost prescribed,
corresponding to a steep extremum of the line energy. Finite contact-angles
might also occur in symmetric membranes from the recruitment of impurities at
the boundary.
