The Central Aspects of Pain in the Knee (CAP-Knee) questionnaire; a mixed-methods study of a self-report instrument for assessing central mechanisms in people with knee pain. Issue 6 (June 2021)

• Record Type: Journal Article
• Authors: Akin-Akinyosoye, K.; James, R.J.E.; McWilliams, D.F.; Millar, B.; das Nair, R.; Ferguson, E.; Walsh, D.A.
• Is Part Of: Osteoarthritis and cartilage. Volume 29:Issue 6(2021)
• Page Start: 802
• Page End: 814
• Publication Date: 2021-06
• Subjects: Osteoarthritis -- Central sensitisation -- Knee pain -- Musculoskeletal -- Questionnaire; CAP-Knee Central Aspects of Pain in the Knee -- OA Osteoarthritis -- CS Central Sensitisation -- QST Quantitative Sensory Testing -- MRI Magnetic Resonance Imaging -- PPT Pressure Pain Detection Thresholds -- TS Temporal Summation -- CPM Conditioned Pain Modulation -- IMHW Investigating Musculoskeletal Health and Wellbeing -- DIF Differential item functioning -- CFI Comparative Fit Index -- TFI Tucker Fit Index -- RMSEA Root Mean Square Error of Approximation -- ACR American College of Rheumatology; Osteoarthritis -- Periodicals; Cartilage -- Periodicals; Osteoarthritis -- Periodicals; Cartilage -- Periodicals; Arthrose -- Périodiques; Articulations -- Maladies -- Périodiques; 616.7223005
• DOI: 10.1016/j.joca.2021.02.562
• Languages: English
• ISSNs: 1063-4584

Abstract

Summary: Objectives: Pain is the prevailing symptom of knee osteoarthritis. Central sensitisation creates discordance between pain and joint pathology. We previously reported a Central Pain Mechanisms trait derived from eight discrete characteristics: Neuropathic-like pain, Fatigue, Cognitive-impact, Catastrophising, Anxiety, Sleep disturbance, Depression, and Pain distribution. We here validate and show that an 8-item questionnaire, Central Aspects of Pain in the Knee (CAP-Knee) is associated both with sensory- and affective- components of knee pain severity. Methods: Participants with knee pain were recruited from the Investigating Musculoskeletal Health and Wellbeing study in the East Midlands, UK. CAP-Knee items were refined following cognitive interviews. Psychometric properties were assessed in 250 participants using Rasch-, and factor-analysis, and Cronbach's alpha. Intra-class correlation coefficients tested repeatability. Associations between CAP-Knee and McGill Pain questionnaire pain severity scores were assessed using linear regression. Results: CAP-Knee targeted the knee pain sample well. Cognitive interviews indicated that participants interpreted CAP-Knee items in diverse ways, which aligned to their intended meanings. Fit to the Rasch model was optimised by rescoring each item, producing a summated score from 0 to 16. Internal consistency was acceptable (Cronbach's alpha = 0.74) and test–retest reliability was excellent (ICC2, 1 = 0.91). Each CAP-Knee item contributed uniquely to one discrete 'Central Mechanisms trait' factor. High CAP-Knee scores associated with worse overall knee pain intensity, and with each of sensory- and affective- McGill Pain Questionnaire scores. Conclusion: CAP-Knee is a simple and valid self-report questionnaire, which measures a single 'Central Mechanisms' trait, and may help identify and target centrally-acting treatments aiming to reduce the burden of knee pain.