A clinical assessment tool to improve the use of pain relieving treatments in knee osteoarthritis

Purpose: Approximately 1 in 4 individuals in the UK over the age of 55 experience knee pain (KP), predominantly due to osteoarthritis (OA). Following treatment targeted at the affected knee, pain relief is reported in only 60%–80% of individuals with painful knee OA. This suggests that mechanisms occurring within the central nervous system (central mechanisms) also influence the KP experience. Although reduced pressure pain detection thresholds (PPTs) at sites distal to the affected joint can indicate central mechanisms, application of PPTs to clinical practice and population-based studies is limited. A feasible, validated questionnaire-based tool to help identify people with KP who may benefit more from centrally acting treatments could prove useful. This study aimed to develop a self-report scale which represents traits associated with central mechanisms in people with KP.Methods: Participants: 9506 individuals completed the Knee Pain and related health In the Community (KPIC) baseline survey. 2152 participants reporting KP were included in this study. 322 individuals with current KP and 98 with no pain undertook PPT assessment at the proximal tibia, distal to the index knee. Questionnaires: The KPIC baseline survey included self-report questionnaires for pain catastrophizing (Pain Catastrophizing Scale), pain patterns (ICOAP), neuropathic-like pain (modified pain DETECT), quality of life (SF-12), and mental health (Hospital Anxiety and Depression Scale). Also included were individual questions addressing the presence and onset of KP, pain severity, risk factors for KP and/or OA, fatigue, cognitive impact, pain distribution (Manikin), sleep. Item Selection: Items related to central mechanisms were selected according to predefined criteria (See Fig. 1): (i) strength of association to constructs measured by the host scale, using exploratory structural equation modelling (ESEM); (ii) expert opinion on relevance to central mechanisms (inter-rater agreement k* ≥ 0.60); (iii) adequate targeting indicated b