Pain sensitisation and the risk of poor outcome following physiotherapy for patients with moderate to severe knee osteoarthritis: protocol for a prospective cohort study
INTRODUCTION
Pain is the dominant symptom of knee osteoarthritis (OA), and recent evidence suggests factors outside of local joint pathology, such as pain sensitisation, can contribute significantly to the pain experience. It is unknown how pain sensitisation influences outcomes from commonly employed interventions such as physiotherapy. The aims of this study are, first, to provide a comprehensive description of the somatosensory characteristics of people with pain associated with knee OA. Second, we will investigate if indicators of pain sensitisation in patients with knee osteoarthritis are predictive of non-response to physiotherapy.


METHODS AND ANALYSIS
This is a multicentre prospective cohort study with 140 participants. Eligible patients with moderate to severe symptomatic knee osteoarthritis will be identified at outpatient orthopaedic and rheumatology clinics. A baseline assessment will provide a comprehensive description of the somatosensory characteristics of each participant by means of clinical examination, quantitative sensory testing, and validated questionnaires measuring pain and functional capacity. Participants will then undergo physiotherapy treatment. The primary outcome will be non-response to physiotherapy on completion of the physiotherapy treatment programme as defined by the Osteoarthritis Research Society International treatment responder criteria. A principal component analysis will identify measures related to pain sensitisation to include in the predictive model. Regression analyses will explore the relationship between responder status and pain sensitisation while accounting for confounders.


ETHICS AND DISSEMINATION
This study has been approved by St James' Hospital/AMNCH Research Ethics Committee and by the St Vincent's Healthcare Group Ethics and Medical Research Committee. The results will be presented at international conferences and published in a peer review journal.


TRIAL REGISTRATION NUMBER
NCT02310945.