Complications of joint fusions can include those applicable to any surgery such as bone and/or soft-tissue infection, wound dehiscence, and failure of fixation. Other complications are specific to fusion procedures and would include malalignment, proximal or distal joint deterioration, and delayed union or nonunion. The latter negative outcomes can occur from medical comorbidities, patient noncompliance, or inappropriate fixation. This article addresses many of these complications including techniques for evaluation, accurate diagnosis, and current treatment options. Special attention is paid to the subject of nonunion, as it is one of the most common and difficult adverse outcomes of arthrodesis procedures.