Application of the IASP Grading System to Identify Underlying Pain Mechanisms in Patients with Knee Osteoarthritis: A Prospective Cohort Study.

This study aimed to apply the International Association for the Study of Pain (IASP) grading system for identifying nociplastic pain in knee osteoarthritis (KOA) awaiting total knee arthroplasty (TKA) and propose criteria to finetune decision-making. Additionally, the study aimed to characterize a 'probable' versus 'no or possible' nociplastic pain mechanism using biopsychosocial variables and compare both groups in their one-year post-TKA response. A secondary analysis of baseline data of a longitudinal prospective study involving 197 KOA patients awaiting total knee arthroplasty in Belgium and the Netherlands was performed. Two approaches, one considering four and the other three pain locations (step 2 of the grading system), were presented. Linear mixed model analyses were performed to compare the 'probable' and 'no or possible' nociplastic pain mechanism groups for several preoperative biopsychosocial-related variables and one-year postoperative pain. Also, a sensitivity analysis, comparing exclusively 'probable' versus 'no' nociplastic pain mechanism groups, was performed. Thirty (15.22% - approach four pain locations) and 46 (23.35% - approach three pain locations) participants were categorized under 'probable' nociplastic pain. Irrespective of the pain location approach or sensitivity analysis, the 'probable' nociplastic pain group included more woman, were younger, exhibited worse results on various preoperative pain-related and psychological variables, and had more pain one-year post-TKA compared to the other group. This study proposed additional criteria to finetune the grading system for nociplastic pain (except for discrete/regional/multifocal/widespread pain) and characterized a subgroup of KOA patients with 'probable' nociplastic pain. Future research is warranted for further validation.

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Copyright © 2024 The Author(s). Published by Wolters Kluwer Health, Inc.

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Funding: This project is sponsored by ‘Bijzonder Onderzoeksfonds (BOF) (PS ID: 42517, 2020)’ of the University of Antwerp Belgium and ‘Fonds wetenschappelijk onderzoek (FWO) (11E5722N, 2020)’ Flanders Belgium. Author A. Foubert was sponsored by BOF (DOCPRO 40017, 2019) and author R.J.E.M. Smeets receives a grant of the Global Awards for Advancing Chronic Pain Research (ADVANCE) (ID#70107413, 2021), however these last two grants are not used for current study. The authors have no conflicts of interest to declare. FUNDING AND CONFLICT OF INTEREST: This project is sponsored by ‘Bijzonder Onderzoeksfonds (BOF) (PS ID: 42517)’ of the University of Antwerp Belgium and ‘Fonds wetenschappelijk onderzoek (FWO) (11E5722N)’ Flanders Belgium. Author A. Foubert was sponsored by BOF (DOCPRO 40017) and author R.J.E.M. Smeets receives a grant of the Global Awards for Advancing Chronic Pain Research (ADVANCE) 2021 ID#70107413, however these last two grants are not used for current study.