LoW back pain is a commo'n, recurrent problem, with many sufferers going on to develop long-term disability and work absence. A number of potential patho- ' anatomical pathways may give rise to low back pain, although the aetiology of a specific episode is often unclear. Management options range from simple analgesia and physiotherapy, to major spinal surgery.Clinical trials often fail to show significant long term differences in outcome between treatment options for low back pain. Measuring the course of this fluctuating condition is problematic, and often what matters to patients is not reflected in standardised clinical outcomes. This thesis describes the development of an individualised approach to outcome measurement which captures changes that are important to patients with low back pain.