The relationship between inadequate response to physical therapy and central sensitization in patients with knee osteoarthritis: A prospective cohort study

Objectives: This study aims to investigate the relationship between physical therapy response and the presence of central sensitization (CS) in patients with painful knee osteoarthritis (OA). Patients and methods: Between May 2019 and March 2020, a total of 84 patients with knee OA (12 males, 72 females; mean age: 60.7±7.7 years; range 50 to 74 years) and 30 age and sex-matched controls (6 males, 24 females; mean age: 59.2±8.9 years; range 50 to 75 years) were included in this study. Knee pain and functional status were evaluated by Visual Analog Scale (VAS) and Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC). Structural damage was assessed by knee radiography. The Central Sensitization Inventory (CSI), Beck Depression Inventory (BDI), Insomnia Severity Index (ISI), Pain Catastrophizing Scale (PCS), and PainDETECT Questionnaire (PDQ) were applied at baseline. Pain pressure thresholds (PPTs) of the patients were measured and compared with the control group. All patients underwent a total of 15 sessions of physical therapy program for five sessions/weekly. After treatment, the patients were divided into two groups as responders and non-responders according to the Osteoarthritis Research Society International (OARSI) criteria. Results: The CSI score of the patients in non-responder group was significantly higher compared to the responder group (p=0.004). Using a cut-off value of ≥40, the proportion of patients with CSI scores of ≥40 was significantly lower in the responder group compared to non-responder group (p=0.021). The PPT measurement values were significantly lower in the non-responder group compared to the responder and control groups (p <0.01). There was a significant difference in the frequency of hyperalgesia between the groups (p=0.021). Central sensitization and depression were the most significant predictors of non-response to physical therapy (p=0.045 and p=0.024, respectively). Conclusion: Our study results suggest the presence of CS and depression may result in an inadequate response to physical therapy in patients with knee OA. Clinicians should consider the findings of CS and depression in treatment planning.