Pain Sensitization and Outcome Following Physiotherapy in Patients With Knee Osteoarthritis

Pain is the dominant symptom of knee osteoarthritis and recent evidence suggests factors outside of local joint pathology, such as pain sensitization, can contribute significantly to the pain experience. It is unknown how pain sensitization influences outcomes from commonly employed interventions such as physiotherapy. The aims of this study are, firstly to identify people with knee OA who display signs and symptoms associated with pain sensitization using clinical tools and quantitative sensory testing. Secondly, we will investigate if indications of pain sensitization at baseline are associated with poor outcome following physiotherapy. Methods and analysis: This is a multi-centre prospective cohort study with 140 participants. Eligible patients with moderate/severe symptomatic knee osteoarthritis will be identified at hospital outpatient 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, in line with current clinical guidelines. Follow-up post physiotherapy treatment (estimated to be at 3 months) will assess pain, disability (sub-scales of Western Ontario and McMasters University Score Osteoarthritis Index) and participants' global rating of change. These primary outcome measures will dichotomise participants into treatment 'responders' and 'non-responders' according to the Osteoarthritis Research Society International (OARSI) treatment responder criteria. For data analysis results from pressure pain thresholds, temporal summation and conditioned pain modulation will create a composite score of pain sensitization. Logistic regression will explore the relationship between response to physiotherapy and pain sensitization at baseline while accounting for various cofounders.