Proximal translation of the radius is a complication of radial head fractures that occurs in association with disruption of the longitudinal soft-tissue stabilizers of the forearm. The sequelae of this process include debilitating wrist and elbow pain secondary to ulnocarpal and radiocapitellar abutment as well as loss of grip strength. When radioulnar dissociation is recognized early, treatment involves prevention of proximal radial migration by preservation of the radial head and stabilization of the distal radioulnar joint. When primary bony repair of the radial head is not feasible, prosthetic replacement of the radial head is necessary to prevent proximal radial migration. Management is complex in chronic cases in which longitudinal radioulnar dissociation is diagnosed after radial migration has occurred. Treatment goals include normalization of the radioulnar relationship and prevention of further migration. Although several reconstructive treatment options are available, no clear solutions exist, and long-term prognosis is guarded. Therefore, early recognition of longitudinal forearm instability is critically important.