P. Albano and P.
Cannarsa proved in 1999 that, under some applicable conditions, singularities of semiconcave functions in Euclidean n-dimensional space propagate along Lipschitz arcs. Further regularity properties of these arcs were proved by P.
Cannarsa and Y. Yu in 2009.
We prove that, for n=2, these arcs are very regular: they have finite turn.