Low back pain (LBP) is a clinically important secondary impairment following lower-extremity trauma, which can negatively affect the quality of life for the injured Service Member (SM). To develop targeted interventions for preventing and/or controlling LBP among SMs with lower-extremity trauma, it is critical to first understand more completely the underlying mechanism(s) linking lower-extremity amputation/injury with increased LBP risk. As such, the overall objective of this research is to identify the relationship(s) between traumatic lower-extremity amputation/injury and LBP via changes in spine mechanics and spine health, two important factors associated with LBP risk. Using a novel set of clinical, experimental, and computational methods, we expect to demonstrate a positive association between abnormal spine mechanics (i.e., increased spinal loads), that over time, negatively affect spine health and increase LBP risk among SMs with lower-extremity trauma. A better understanding of the relationship(s) between lower-extremity trauma and spine mechanics and spine health is critical not only for prevention (either proactive or reactive), but also for guiding the development of alternative rehabilitation or intervention strategies for preventing and/or controlling spinal loads in this population. The current work will promote and improve long-term functional outcomes for SMs with lower-extremity trauma by helping to mitigate a significant secondary impairment with a substantial impact on their daily activities.