Date of Award

2024

Degree Name

Doctor of Philosophy (School of Physiotherapy)

Schools and Centres

Physiotherapy

First Supervisor

Benedict Wand

Second Supervisor

William Gibson, Mervyn Travers

Third Supervisor

Myles Murphy

Fourth Supervisor

Dana Hince

Abstract

Knee osteoarthritis poses a substantial and escalating socioeconomic burden globally, exacerbated by demographic trends towards an aging population, sedentary lifestyles and increasing obesity rates. Defined by knee pain and functional limitations (Wood et al., 2023; Zhang, Doherty, et al., 2010), traditional approaches have viewed knee OA related pain and disability primarily through a biomedical lens, linking symptoms directly to structural damage and advocating surgical interventions such as total knee arthroplasty to address presumed causative pathology (Bunzli et al., 2019; Darlow et al., 2018). Despite the capacity of surgery to ameliorate structural pathology, patient centred outcomes vary considerably. Up to 30% of patients report experiencing suboptimal post-operative results secondary to persistent post-operative pain or dissatisfaction with outcome (Beswick et al., 2012; Bierke & Petersen, 2017; Brander et al., 2003; Ditton et al., 2020; Khatib et al., 2020; Koga et al., 2024; Wylde et al., 2018).

Recent insights help clarify why treatment that addresses only structural pathology fail up to a third of surgical recipients. It is now well recognised that knee pain reflects a complex interplay of biological, psychological, and social factors, and that structural damage is only a part of the clinical picture (Lotze, 2007; Moseley, 2017). This holistic perspective characterises knee OA as a multifaceted condition, influenced by biopsychosocial factors that modulate pain sensitivity and shape behavioural responses (Caneiro et al., 2020; Hunter, 2018; Kittelson, George, et al., 2014). Inspired by the Fit-For-Purpose Model (Wand et al., 2022) initially developed for chronic low back pain, this thesis aims to investigate cognitive, perceptual and behavioural factors aligned with the Fit-For-Purpose Model in the context of knee OA. The chapters of this thesis will each address specific aspects of knee OA and post-total knee arthroplasty outcomes. Chapter 2 provides the systematic review and meta-analysis protocol exploring functional improvements post total knee arthroplasty, comparing self-reported and performance-based measures of function. Chapter 3 presents the review and its findings, highlighting the less-than-ideal functional outcomes seen post knee replacement. Chapter 4 introduces two innovative tests – the Perceived Knee Size Task and the Fremantle Fragility Index. These tests aim to fill gaps in the current assessment of people with symptomatic knee OA by providing fine grained psychophysical assessments of perceptual and conceptual body representations. This chapter provides the first description of these two tasks as well as offering the first normative data and preliminary evidence of reliability. Chapter 5 focuses on a self-reported assessment of perceptual body representation specific to the knee. There is data on the measurement properties of translated versions of the Fremantle Knee Awareness Questionnaire, but no evaluation of the original English language version. This chapter explores the structural and construct validity of this questionnaire. Noting that there is currently no self-reported measure of conceptual body representation, Chapter 6 presents a short report on the Fremantle Knee Fitness Score (FKFS), a simple tool I developed to assess the views people hold regarding the degree of structural damage to their knee and the fragility of their knee. Finally, Chapter 7 integrates the Fremantle Knee Awareness Questionnaire and the Fremantle Knee Fitness Score with existing self-reported measures to explore the cross-sectional relationships between Fit-For-Purpose Model aligned factors and pain/disability in knee OA. This comprehensive analysis aims to elucidate how psychological, perceptual, and physical factors contribute to the chronicity of knee OA and inform tailored treatment approaches.

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