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Determinants and management of the progression of osteoarthritis in older adults

Munugoda, IP ORCID: 0000-0001-5075-6760 2020 , 'Determinants and management of the progression of osteoarthritis in older adults', PhD thesis, University of Tasmania.

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Abstract

Osteoarthritis (OA) is one of the most common musculoskeletal disorders, of which knee and
hip OA account for the biggest burden of disease. It is a multifactorial disease with many risk
factors and determinants such as age, sex and lifestyle factors including obesity, physical
activity and diet being associated with both the onset and progression of the disease. Owing to
the complex nature of the disease, no definitive treatment is available for OA. In order to better
manage and treat this condition, it is important to improve the understanding of the lifestyle
and structural factors related to the progression of the disease as well as the management of
these factors. Therefore, the overall aims of this thesis were to identify determinants, risk
factors and potential management strategies for the progression of OA in older adults.
In this thesis, data from two studies were utilised. The first study was a prospective population-based
cohort study of older adults who were between 50 and 80 years of age named the
Tasmanian Older Adults Cohort Study (TASOAC). The participants for the study were selected
from sex-stratified random sampling from the electoral role in Southern Tasmania (population
229,000). Data was collected at baseline and at 2.5, 5 and 10 years after the initial clinic
assessment. At baseline, information on objective measures of body composition using body
mass index (BMI) obtained by weight and height measures and fat and lean mass using dual-energy
x-ray absorptiometry (DXA) were obtained. Pedometer measured ambulatory activity
(AA) was recorded at baseline and socioeconomic status (SES) of the participants was
collected by matching each participant’s residential address to the corresponding Australian
Bureau of Statistics (ABS) Census Collection District to determine the Socio-Economic
Indexes for Areas (SEIFA) value from the 2001 census. Knee pain of the participants at
baseline and the 10-year follow-up was collected using Western Ontario and McMaster
Universities Osteoarthritis Index (WOMAC). In addition, various imaging modalities such as
radiography of the knee and hip at baseline and Magnetic Resonance Imaging (MRI) of the
knee at baseline and the 10-year follow-up were conducted. Based on the radiographs, the
status of radiographic OA (ROA) was defined. Utilising the knee MRI of the participants,
several structural features such as Tibial cartilage volume and bone-marrow lesions (BMLs)
were measured. The incidence of primary (first-time) total knee replacements (TKR) and total
hip replacements (THR) were determined by data linkage to the Australian Orthopaedic
Association National Joint Replacement Registry (AOANJRR).
The second study was a single-blind, single-center, 18-month, randomized controlled trial of
older adults aged over 55 years named the Intensive Diet and Exercise for Arthritis trial
(IDEA). The study was designed to evaluate the effects of weight loss obtained by diet and/or
exercise on OA outcomes of the knee. Participants were eligible for the study if they had
Kellgren-Lawrence grade (KLG) 2-3 tibiofemoral or tibiofemoral with patellofemoral OA of
at least one knee, pain on most days due to knee OA, a BMI between 27 and 41 kg/m2 and a
sedentary lifestyle, i.e. <30 min/week of formal exercise over the past 6 months. The
participants were randomized to one of three 18-month interventions: exercise only, diet only
or diet+exercise. MRI was obtained in a random subsample (n=105) of the IDEA participants
at baseline and the 18-month follow-up. Using these MRIs, the medial and lateral menisci were
segmented, and position and size parameters were measured quantitatively, along with
semiquantitative extrusion measures.
In the first study of this thesis, we assessed the association between SES and time to THR and
TKR due to OA in older adults. The results showed that less disadvantaged participants were
less likely to have a THR (i.e. less disadvantaged participants had a longer time to THR) in
comparison to the most disadvantaged participants; however, this association was attenuated
adjustments for hip pain and hip ROA. This suggests that time to joint replacements is
determined according to the symptoms/need of the participants rather than their SES, indicating
reductions in expected disparity between SES and time to joint replacement. This further
confirms the usefulness of using joint replacement as a marker of end-stage OA in the knee
and hip.
The second study evaluated the association between AA and body composition measures such
as BMI, fat mass, lean mass and waist circumference with the risk of TKR and THR due to OA
in a population of community-dwelling older adults. The results showed that AA was related
to a higher risk of TKR and a lower risk of THR. BMI, total fat, trunk fat mass and waist
circumference were associated with a higher risk of TKR although body composition measures
were not related to THR. These finding suggest that habitual activity and obesity may have
different causal pathways for OA progression in knee and hip joints.
In the third study, we investigated the prospective associations between baseline hip
morphology defined as hip shape modes using Statistical Shape Modelling (SSM) and the
progression of several clinical and MRI-based knee OA outcomes in older adults. The results
showed that longer, wider femoral neck and larger femoral head (mode 1) was associated with
increased risk of worsening knee pain, whereas wider femoral neck (mode 9) was related to
reduced risk of worsening knee pain. Larger greater trochanter (mode 7) and greater acetabular
coverage (mode 10) were linked to lower cartilage volume loss, while shorter, wider femoral
neck (mode 9) was associated with increased cartilage volume loss. Smaller femoral head
(mode 4) was related to increased risk of worsening BMLs. Greater acetabular coverage (mode
10) was associated with a reduced risk of TKR. Overall these findings may imply that hip shape
variations are important in the long-term progression of knee OA in older adults.
The fourth study assessed whether weight loss achieved by diet and/or exercise is related to
meniscus extrusion parameters in the medial and lateral meniscus over 18 months. The results
showed that weight loss was related to less progression of medial meniscus extrusion as
measured by the maximum and mean extrusion distances. Weight loss was not associated with
lateral meniscus position, medial or lateral meniscus size or with semiquantitative measures.
These findings suggest that weight loss is related to beneficial modifications of medial
meniscus extrusion in older adults.
In conclusion, this sequence of studies first established the importance of TKR and THR as a
marker of end-stage OA and showed that habitual activity and obesity act differently on end-stage
OA of the hip and knee joints. Additionally, variations in hip shape may be an important
structural feature that is associated with the progression of knee OA. Lastly, weight loss was
related to less progression of meniscus extrusion in older adults with knee OA. Overall, the
findings of this thesis suggest the importance of certain lifestyle factors. Better management of
these factors may help to reduce OA progression in older adults.

Item Type: Thesis - PhD
Authors/Creators:Munugoda, IP
Keywords: Osteoarthritis, knee cartilage, total knee replacement, total hip replacement, physical activity, obesity, weight loss, magnetic resonance imaging
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Copyright 2019 the author

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