The increased utilization of manipulators in hazardous or hard-to-reach environments have led to a corresponding increase on the study of fault tolerant control methods for these mechanisms, ranging from robot design and trajectory planning to fault detection and isolation and post-failure control algorithms. In this article we focus on post-failure control of a mechanical manipulator from the point of view of optimal control, and present a novel method for controlling the positions of the failed, passive joints, in an optimal way. Although the optimization is performed locally, the results indicate the validity and feasibility of the proposed theory.