Disclosures: Joana Barroso, MD MSc: Nothing to disclose

Objective: Determine how distinct pain scales relate to different aspects of pain experience in osteoarthritis (OA).

Design: Cross-sectional cohort study of knee OA patients, using four different outcomes, both general and OA specific.

Setting: Outpatient Orthopedic Surgery Clinic.

Participants: 95 OA patients with Kellgren-Lawrence grade 3 or 4 and indication for total knee replacement.

Interventions: We collected demographic data (age, gender, education), physical performance tasks (6-minute walking test, stand-up and go test), radiographic OA severity (Kellgren-Lawrence scale) and applied multiple questionnaires, covering pain characteristics, anxiety and depression, catastrophizing, health and life quality (MPQ, DN4, HADS, PCS, KOOS, BPI, SF-36).

Main Outcome Measures: Pain intensity measured by three general pain scales – NRS; BPI pain severity and SF36 bodily pain (here relating to the articular pain) and one specific instrument – KOOS pain. We studied the interrelationship of these pain measures and evaluated their association with a large number of clinical and psychosocial variables, analyzing common and singular influences.

Results: Correlations between pain measures were significantly positive (P<.001), with varying strength among scales (r=0.162 – 0.792). Principal component analysis was performed on questionnaires and physical performance tests, revealing 5 components accounting for 70% of the variance. These were used to model pain outcome scales, together with demographic and radiographic data. Hierarchical regression models showed pain quality (component formed by DN4 and McGill sensory quality) as the common dominant factor influencing all scales. Each scale then showed unique associations with distinct factors: BPI severity with pain catastrophizing, KOOS Pain with physical performance and SF-36 pain with Health Status (all models, adjusted R2=.229 – .573, P <.001).

Conclusions: Pain quality seems to be a common denominator influencing pain rating across scales. However, association with unique features of pain experience were identified for each scale, rendering heterogeneity among pain outcomes. These findings raise awareness for pain scales employment, equivalence and comparability in OA.

Level of Evidence: Level I

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PM&R Meeting Abstracts - https://pmrjabstracts.org/abstract/pain-measures-in-knee-osteoarthritis-distinct-instruments-distinct-facets-of-pain-experience/