It has been observed that the more visible features of nervous system sensitization are associated with more severe symptomatology, including those with knee osteoarthritis (OA). In clinical practice, more knowledge regarding the role of nervous system sensitization in symptom progression in knee OA would be an added factor. The relation between features of nervous system sensitization and responder status has not been studied in a cohort of individuals with knee OA referred for physiotherapy management.

Lately, a group of researchers conducted a study to determine the independent association between features of nervous system sensitization and clinical outcome (non-response). It was a prospective cohort study, which involved 156 participants suffering from knee OA. The patients were analyzed at baseline and followed up on discharge from physiotherapy. Baseline evaluation before physiotherapy gave complete details regarding somatosensory characteristics of every participant using clinical examination, quantitative sensory testing, and validated questionnaires. General physiotherapy care was given to each participant. Physiotherapy comprised of between four and six sessions out of which exercise, education and self-management advice were the major components. The participants were classified as non-responders or responders on discharging from physiotherapy with use of OMERACT-OARSI criteria responder criteria (based on changes in pain, disability or global rating of change). A hierarchical logistic regression model was prepared to find out whether features of nervous system sensitization added with some significance to a model containing other known predictors of poor outcome. The features include pressure pain thresholds (PPTs), temporal summation (TS), cold hyperalgesia, conditioned pain modulation or Central Sensitization Inventory.

Higher TS and lower PPTs appeared as reliable indicators of poor non-response after receiving physiotherapy from a model that tested for other predictors of poor outcome (comorbidity score, treatment adherence ratio, age, gender, depression). The study estimated that more enhanced TS had more probability of being a non-responder (OR 2.00, 95% CI 1.23 to 3.27). The OR of 0.48 (95% CI 0.29 to 0.81) for PPT. This indicated that higher PPTs were related to decreased probability to be classified as a non-responder. Cold hyperalgesia, conditioned pain modulation, and the Central Sensitization Inventory were not retained in the primary hierarchical model. This model evaluated high sensitivity (88.9%) but modest specificity (52.3%) suggesting these factors may not be useful for predicting the outcome with sufficient accuracy to justify their clinical use.

The study concludes that variables illustrating nervous system sensitization like lower PPTs and enhanced TS possesses the ability to predict nonresponse following physiotherapy independently. This independent relationship points to an underlying explanatory association between maladaptive neuroplastic changes in nociceptive processing and maintenance of on-going pain and disability in knee OA. These preliminary results may have implications for developing therapeutic targets related to the nervous system in the future treatment of knee OA. It is necessary to repeat these results in another cohort and inclusion of a control group would help to understand if features of nervous system sensitization are general prognostic factors or treatment effect modifiers.