For patient after patient seeking to cure chronic back pain, the experience is years of frustration. Whether they strive to treat their aching muscles, bones and ligaments through physical therapy, massage or rounds of surgery, relief is often elusive – if the pain has not been made even worse. Now a new working hypothesis explains why: persistent back pain with no obvious mechanical source does not always result from tissue damage. Instead, that pain is generated by the central nervous system (CNS) and lives within the brain itself.