Curves in Lagrange Grassmannians naturally appear when one studies Jacobi equations for extremals, associated with geometric structures on manifolds. We fix integers di and consider curves (t) for which at each t the derivatives of order i of all curves of vectors (t) (t) span a subspace of dimension di. We will describe the construction of a complete system of symplectic invariants for such parametrized curves, satisfying a certain genericity assumption, and give applications to geometric structures, including sub-Riemannian and sub-Finslerian structures. To cite this article: I. Zelenko, C. Li, C. R. Acad. Sci. Paris, Ser. I 345 (2007). 2007 Acadmie des sciences.