The second variation of energy corresponding to crack length is required in the stability analysis of crack growth. For determining such an energy gradient, an efficient finite element method extending the classical virtual crack extension concept is described in this paper. In elasticity, the method can be used for the prediction of the growth pattern of one single "crack, and especially a system of interacting cracks as well from the results of a single strain-stress analysis. Example computations are performed for (1) a center-cracked plate and (2) a finite width strip containing two interacting cracks. Close agreement between the numerical results give~ by our method and reference solutions has been found in all testing cases.