The effect of linear defects and steps on the magnetocrystalline anisotropy energy of ultrathin films of Co and Fe is self-consistently calculated using an electronic tight-binding theory. The presence of linear defects produces changes in the spontaneous orientation of the magnetic moments and the induced magnetic anisotropy depends, among others, on the relative orientation of the introduced defects with respect to the substrate. A variety of possible situations is also obtained as a function of orientation index in the case of vicinal surfaces. Within our theoretical framework we obtain results that agree well with experiments.