Over the past decade, there have been more than 1,280 service members with amputations resulting from injuries sustained in Iraq and Afghanistan. Current research indicates that the majority of these amputees will suffer from phantom limb pain, defined as the perception of pain in a missing limb. However, despite the wealth of research on phantom limb pain the mechanisms behind the phenomenon remain obscure. Mirror therapy appears to be the most promising therapy to date. The current paper reviews the pivotal theories on phantom limb pain (peripheral, spinal, and psychological factors, the body schema, the neuromatrix, cortical reorganization, pain and proprioceptive memory, and movement) with the hopes of highlighting key gaps in our understanding of the disorder.