Central sensitization (CS) is a phenomenon associated with several medical diagnoses, including postcancer pain, low back pain, osteoarthritis, whiplash, and fibromyalgia. CS involves an amplification of neural signaling within the central nervous system that results in pain hypersensitivity. The purpose of this systematic review was to gather published studies of a widely used outcome measure (the Central Sensitization Inventory [CSI]), determine the quality of evidence these publications reported, and examine the measurement properties of the CSI.