Wireless Mesh Network (WMN) has been recognized as one of the promising technologies to provide wireless broadband access. In addition to the multi-radio multi-channel network architecture often seen in WMNs, employment of directional antennas on each mesh node could further improve the system throughput via alleviating the interference between nearby nodes thus allowing more concurrent transmissions in the network. In this paper, we describe a novel algorithm to produce joint decisions on routing and channel assignment with practical implementation considerations for WMNs with directional antennas. In particular, we formulate this joint optimization problem as a Mixed Integer Programming (MIP) problem with all practical considerations modeled explicitly as MIP constraints. For example, our scheme only considers dual-path routes and one- to-one association between access points and gateway nodes, so as to facilitate its deployment with commercial wireless networking devices such as IEEE 802.11 compliant devices. The objective is to maximize the aggregate system throughput and to provide fair and satisfactory services to all access points. Simulation results show that our scheme (i.e., the solution to the MIP problem) fully exploits the multi-radio multi-channel network architecture and directional antennas in WMNs, and is able to achieve the design objectives with significantly reduced implementation complexity.