A better understanding of the mechanisms of ultrasound propagation in trabecular bone could considerably help improving the quantitative ultrasonic techniques commonly used to assess bone quality. Some phenomena experimentally observed in trabecular bone remain poorly understood, such as the possible propagation of two compressional waves with different velocities. In this study, elastic wave propagation has been simulated using a finite-difference time-domain method in two-dimensions. Trabecular bone was modeled by a binary random medium with fully controlled elasticity and anisotropy. To do so, elliptic-shaped patterns were randomly distributed on two-dimensional (2-D) maps with an orientation ensuring global anisotropy. The coherent wave was obtained by averaging over a large number of random maps. Several conditions for the observation of the two waves have been identified: (i) The propagation has to occur in a direction parallel to the main orientation of the medium. (ii) some of the elliptic pattern elements had to be connected, which suggests the importance of a percolation threshold. (iii) It is necessary to take into account shear waves in the solid phase. This suggests that bone microarchitecture parameters (anisotropy and connectivity) could be retrieved from ultrasonic measurements, improving the evaluation of fracture risk.