Every year millions of traumatic brain injuries (TBI) caused by any type of sudden external force upon the head occur in the United States, accompanied by a range of complex physical, cognitive, behavioral, and emotional problems. The period of time between injury and re-adaptation to social roles is generally labeled rehabilitation as the survivor works to achieve recovery of function. A phemen that has stumped the medical community for decades, and still remains unsolved is how best to foster recovery for TBI individuals, although there is general agreement that motivation plays a key role. This study was designed to address the following research question: What is the genesis and nature of the motivation experienced by individuals with TBI in rehabilitation? The author sought to understand the motivational factors and to generate a model of these factors grounded in the data. The phemelogical approach of grounded theory was used to examine the experiences of individuals with TBI as they constructed meaning from events and interactions in their rehabilitation setting. For individuals with TBI in this study, the outcome of motivation was engagement in rehabilitation programs. The data in this study suggested that participation was achieved as a result of a synergy that was interactionally created by four contextual categories: one's perception of self, perception of recovery, vision, and personal interactions. This synergy was called momentum, the central phemen. These categories are presented metaphorically in a gyroscopic model. Momentum generated continued rehabilitation participation, that, in turn, enabled the client to return to community life at the highest level possible.