"An impediment to living life": why and how should we measure stiffness in polymyalgia rheumatica?

Sarah Louise Mackie,Colin Pease,John Day,Marion Newton,Marianne Morris,Margaret Walsh,Rodney Hughes,John Kirwan,Sam Eldabe

doi:10.1371/journal.pone.0126758

Abstract

ObjectivesTo explore patients’ concepts of stiffness in polymyalgia rheumatica (PMR), and how they think stiffness should be measured.MethodsEight focus groups were held at three centres involving 50 patients with current/previous PMR. Each group had at least one facilitator and one rapporteur making field notes. An interview schedule was used to stimulate discussion. Interviews were recorded, transcribed and analysed using an inductive thematic approach.ResultsMajor themes identified were: symptoms: pain, stiffness and fatigue; functional impact; impact on daily schedule; and approaches to measurement. The common subtheme for the experience of stiffness was “difficulty in moving”, and usually considered as distinct from the experience of pain, albeit with a variable overlap. Some participants felt stiffness was the “overwhelming” symptom, in that it prevented them carrying out “fundamental activities” and “generally living life”. Diurnal variation in stiffness was generally described in relation to the daily schedule but was not the same as stiffness severity. Some participants suggested measuring stiffness using a numeric rating scale or a Likert scale, while others felt that it was more relevant and straightforward to measure difficulty in performing everyday activities rather than about stiffness itself.ConclusionsA conceptual model of stiffness in PMR is presented where stiffness is an important part of the patient experience and impacts on their ability to live their lives. Stiffness is closely related to function and often regarded as interchangeable with pain. From the patients’ perspective, visual analogue scales measuring pain and stiffness were not the most useful method for reporting stiffness; participants preferred numerical rating scales, or assessments of function to reflect how stiffness impacts on their daily lives. Assessing function may be a pragmatic solution to difficulties in quantifying stiffness.

Highlights

Polymyalgia rheumatica (PMR) is an inflammatory musculoskeletal disease that affects older people
Diurnal variation in stiffness was generally described in relation to the daily schedule but was not the same as stiffness severity
A conceptual model of stiffness in PMR is presented where stiffness is an important part of the patient experience and impacts on their ability to live their lives

Summary

Introduction

Polymyalgia rheumatica (PMR) is an inflammatory musculoskeletal disease that affects older people. Core clinical features for the diagnosis of PMR include bilateral shoulder and/or hip pain, morning stiffness, and abnormal inflammatory markers such as the erythrocyte sedimentation rate [1]. “Morning stiffness” is considered an important diagnostic clue to presence of inflammatory symptoms, to differentiate “inflammatory” disorders such as PMR and rheumatoid arthritis (RA) from “non-inflammatory” disorders such as osteoarthritis [2]. PMR is treated with glucocorticoids (steroids), often for several years [2,3], at the cost of a significant burden of risks and adverse effects in this age group.[1] Monitoring disease activity in treated patients is important, and may require physicians to ask different questions than they would use for diagnosis. Patient-reported outcome measures that capture the impact of the disease on patients’ lives are required for a core outcome set [4] that will allow optimal treatment strategies to be developed

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