Pain, the most urgent of symptoms usually signals the presence of potential or on-going injury to tissue which requires attention. The warning that pain provides is, therefore, a good thing and in a way friendly. When pain continues or resumes after the healing process of injury is complete, it is no longer signalling on-going tissue damage but becomes a disease in its own right. That, in essence, is the presentation of most chronic pain syndromes referred to Pain Clinics for investigation and treatment.