A guide for cutting a bone comprising an anterior portion and a distal portion orientated at about a right angle to the anterior portion. The distal portion includes a guiding side, a distal surface at the guiding side, a box-cut shaped opening defined by the guiding side, a plurality of first cutting surfaces disposed at the guiding side at an acute angle relative to the distal surface of the guiding side operable to guide a cutting device to the bone to form chamfer cuts in the bone, and a second cutting surface disposed at the guiding side at at least about a right angle to the distal surface operable to guide a cutting device to the bone to form a posterior cut in the bone.