One obstacle to investigating the implications of pain sensitization is reliably identifying it in the clinical setting. Clinical criteria proposed for assessing central sensitization rely principally on the clinician's subjective interpretation of patient symptoms. Although useful clinically, for research purposes more objective measures are preferable. Due to the complexity of the pain experience it is inadvisable to rely on any single test to reflect peripheral and central pain mechanisms. A multi-tissue assessment using a multi-modal stimuli approach has been advocated, and will be adopted in this study. Recognised features of central and peripheral sensitization previously identified in knee OA patients will be incorporated into this study and these include extended areas of hyperalgesia, enhanced temporal summation, and dysfunctional conditioned pain modulation.