The epidemiology and interaction of knee alignment and body mass on knee osteoarthritis

453 Pages·2016·17.04 MB·English

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UNIVERSITY OF SOUTHAMPTON

FACULTY OF MEDICINE

The epidemiology and interaction of knee alignment and
body mass on knee osteoarthritis

by

Lyndsey Goulston
Thesis submitted for the degree of Doctor of Philosophy

September 2015

ABSTRACT
UNIVERSITY OF SOUTHAMPTON
FACULTY OF MEDICINE
Human Development and Health
Doctor of Philosophy
THE EPIDEMIOLOGY AND INTERACTION OF KNEE ALIGNMENT AND BODY
MASS ON KNEE OSTEOARTHRITIS
By Lyndsey Goulston
The growing prevalence of knee osteoarthritis (KOA) is fuelled by the rising
obesity epidemic and an ageing population. The lack of a KOA cure drives the
need to identify prevention strategies with alternative treatments to surgery a
priority. This requires careful investigation of risk factors and their interaction.
Knee mal-alignment and excess body mass are KOA risk factors but their
combined effect is less understood.
These five studies examine knee alignment and body mass as separate risk
factors, describing their natural history and their association with prevalence
and incidence of symptomatic radiographic knee osteoarthritis (SRKOA),
radiographic knee osteoarthritis (RKOA) and knee pain outcomes in a long-
standing female cohort. The cross-sectional interaction of these risk factors
and outcomes is examined. One-point (1P) versus two-point (2P) anatomic axis
(AA) knee alignment measurements, and body mass index (BMI) versus waist
circumference (WC) measurements are also compared.
Differences between 1P and 2P measurements indicate method specific
alignment categories are required. Improvements are identified in AA angle
measurement that require further validation to establish a gold standard AA
alignment method. Changes in AA alignment over 10 years were small, but
limited by identification of rotated knees.
Over 19 years the tripling amount of obese women, was associated with
increased prevalence and incidence of SKROA, RKOA and knee pain. WC
measurement offers no advantage over BMI in predicting SRKOA, but it could
be substituted where height or weight measurement is difficult.
Results suggest a cross- sectional interaction between BMI and alignment with
SRKOA and RKOA but not with knee pain, indicating that it may be driven by
structure. This is important for targeting timely treatment of these risk
factors.
This new knowledge should assist in identification of individuals who would
benefit from early intervention and treatment, to reduce pain, suffering and
high future costs of KOA.
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List of contents
ABSTRACT ................................................................................................................................ i
List of contents .................................................................................................................. iii
List of tables ...................................................................................................................... xv
List of figures ................................................................................................................... xix
List of publications & presentations ............................................................... xxiii
Declaration of authorship ........................................................................................ xxv
Acknowledgements ................................................................................................... xxvii
List of abbreviations ................................................................................................. xxix
1. Chapter 1: Introduction ........................................................................................ 1
1.1 Introduction ....................................................................................... 1
2. Chapter 2: Background & literature review .............................................. 3
2.1 Introduction ....................................................................................... 3
2.2 Osteoarthritis ..................................................................................... 3
2.2.1 Defining knee osteoarthritis terms ............................................... 4
2.2.2 Diagnostic criteria ........................................................................ 6
2.2.3 Classification ................................................................................ 7
2.2.3.1 Radiographic classification ..................................................... 8
2.2.4 Prevalence .................................................................................. 11
2.2.5 Incidence ................................................................................... 14
2.2.6 Progression ................................................................................ 15
2.2.7 Impact on the individual ............................................................. 17
2.2.8 Economic impact ........................................................................ 19
2.3 Aetiology & pathology ...................................................................... 21
2.3.1 Pathological features .................................................................. 22
2.3.1.1 Articular cartilage ................................................................ 24
2.3.1.2 Sub-chondral bone ............................................................... 25
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2.3.1.3 Osteophytes ......................................................................... 25
2.3.1.4 Synovium ............................................................................. 26
2.3.1.5 Meniscal damage .................................................................. 26
2.3.1.6 Ligamentous laxity ............................................................... 27
2.3.1.7 Muscle weakness .................................................................. 27
2.3.2 Causes of joint pain .................................................................... 28
2.4 Risk factors ....................................................................................... 29
2.4.1 Systemic risk factors ................................................................... 29
2.4.1.1 Age ...................................................................................... 29
2.4.1.2 Gender ................................................................................. 30
2.4.1.3 Menopause........................................................................... 30
2.4.1.4 Ethnicity ............................................................................... 31
2.4.1.5 Genetic factors ..................................................................... 31
2.4.1.6 Heberden’s nodes ................................................................ 31
2.4.1.7 Index to ring finger length ratio ........................................... 32
2.4.2 Mechanical risk factors ............................................................... 33
2.4.2.1 Obesity ................................................................................ 33
2.4.2.2 Knee injury ........................................................................... 33
2.4.2.3 Knee joint loading ................................................................ 34
2.4.2.4 Knee alignment .................................................................... 35
2.4.2.5 Muscle strength ................................................................... 35
2.4.3 Summary .................................................................................... 36
2.5 Obesity as a KOA risk factor .............................................................. 36
2.5.1 The burden of obesity ................................................................ 37
2.5.2 Prevalence .................................................................................. 38
2.5.3 Childhood obesity ...................................................................... 39
2.5.4 Reducing obesity ........................................................................ 42
2.5.5 Measuring obesity ...................................................................... 44
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2.5.5.1 Body mass index .................................................................. 44
2.5.5.2 Body composition ................................................................ 47
2.5.6 Obesity and KOA associations .................................................... 48
2.5.7 Mechanism of association .......................................................... 50
2.5.7.1 Mechanical loading theory ................................................... 50
2.5.7.2 Metabolic theory .................................................................. 51
2.5.8 Obesity summary ....................................................................... 53
2.6 Knee alignment as a KOA risk factor ................................................. 53
2.6.1 Alignment methods .................................................................... 53
2.6.2 Knee mal-alignment ................................................................... 55
2.6.3 Lower limb alignment ................................................................. 58
2.6.3.1 Mechanical axis & anatomic axis alignment .......................... 58
2.6.3.2 Mechanical axis alignment ................................................... 60
2.6.3.3 Anatomical axis alignment ................................................... 61
2.6.3.4 Comparative alignment studies ............................................ 63
2.6.4 Alignment & KOA associations ................................................... 71
2.6.4.1 Knee alignment and KOA incidence and progression ............ 71
2.6.4.2 Knee alignment & structural features ................................... 74
2.6.4.3 Knee alignment & disease severity ....................................... 77
2.6.4.4 Knee alignment & symptoms ................................................ 78
2.6.5 KneeMorf alignment software ..................................................... 78
2.6.5.1 Computer assisted analysis for measuring knee alignment ... 78
2.6.6 Alignment summary ................................................................... 82
2.7 Risk factor interaction....................................................................... 82
2.7.1 Defining an interaction ............................................................... 83
2.7.2 Understanding interactions between risk factors ........................ 84
2.7.3 Alignment & body mass interaction in KOA ................................ 84
2.7.4 Interaction summary .................................................................. 87
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2.8 Main thesis aim ................................................................................. 88
2.9 Thesis objectives .............................................................................. 88
2.10 Structure of thesis............................................................................. 88
2.11 Scope of thesis ................................................................................. 89
3. Chapter 3: Methodology ................................................................................... 91
3.1 Introduction ...................................................................................... 91
3.2 Main thesis aim & objectives ............................................................. 91
3.3 Study design ..................................................................................... 91
3.3.1 The Chingford 1,000 Women Study ............................................ 91
3.3.2 Study approvals .......................................................................... 95
3.3.3 Recruitment strategy .................................................................. 95
3.3.4 Consent ...................................................................................... 95
3.3.5 Withdrawal of participants .......................................................... 96
3.3.6 Publicity ..................................................................................... 96
3.3.7 Study funding ............................................................................. 97
3.3.8 Data management ...................................................................... 97
3.4 Study population ............................................................................... 98
3.4.1 Inclusion criteria ......................................................................... 98
3.4.2 Exclusion criteria ........................................................................ 98
3.4.3 Bias ............................................................................................ 98
3.5 Data collection .................................................................................. 99
3.5.1 Anthropometry measurements ................................................... 99
3.5.1.1 Weight ................................................................................. 99
3.5.1.2 Height ................................................................................ 100
3.5.1.3 Waist circumference ........................................................... 101
3.5.2 Musculoskeletal questionnaire .................................................. 101
3.5.3 Knee radiographs ..................................................................... 103
3.5.4 Measuring knee alignment ........................................................ 104
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3.5.4.1 Manual measurement ......................................................... 104
3.5.4.2 KneeMorf software ............................................................. 105
3.6 Outcome variables .......................................................................... 111
3.6.1 SRKOA ...................................................................................... 111
3.6.2 RKOA ....................................................................................... 111
3.6.3 Knee pain ................................................................................. 111
3.7 Confounding variables .................................................................... 111
3.7.1 Age .......................................................................................... 113
3.7.2 Body mass index ...................................................................... 113
3.7.3 Knee injury ............................................................................... 113
3.8 Overview of statistical analysis........................................................ 113
3.8.1 Data preparation & analysis software ........................................ 113
3.8.2 Descriptive statistics ................................................................ 114
3.8.3 Agreement statistics ................................................................. 114
3.8.4 Determination of associations .................................................. 115
4. Chapter 4: Alignment pilot studies ......................................................... 117
4.1 Pilot study 1 ................................................................................... 117
4.1.1 Background .............................................................................. 117
4.1.2 Aim .......................................................................................... 118
4.1.3 Method .................................................................................... 118
4.1.4 Analysis ................................................................................... 118
4.1.5 Results ..................................................................................... 120
4.1.6 Conclusion ............................................................................... 130
4.2 Pilot study 2 ................................................................................... 131
4.2.1 Background .............................................................................. 131
4.2.2 Aim .......................................................................................... 132
4.2.3 Method .................................................................................... 132
4.2.4 Analysis ................................................................................... 132
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