| Summary: | Physical activity (PA) is recommended for all adults with osteoarthritis (OA). Adults aged 45 years and over with joint pain, are likely to have already developed OA or are at risk of OA. This thesis examines self-reported PA levels in community dwelling adults aged 45 years and over with joint pain and how PA can be best measured within this population. Self-reported PA levels of 14,212 adults (aged 45 years and over) with and without self-report joint pain demonstrated that adults aged 45 years and over with joint pain are less likely to be active compared to adults with no joint pain (OR= 0.75, 0.68-0.77 95%CI). A systematic review appraised the measurement properties of twenty self-report PA instruments previously used in adult aged 45 years and over and OA or joint pain populations. The International Physical Activity Questionnaire short form (IPAQ-SF) and the Physical Activity Scale for the Elderly (PASE) appeared to be most suitable self-reported PA instruments in joint pain and OA research. An analysis of measurement properties of the IPAQ-SF and PASE was conducted in 525 adults aged 45 years and over consulting primary care with joint pain. Reliability of the IPAQ-SF was lower (r=0.58, p= < 0.01) compared to the PASE (ICC=0.69, 95%CI= 0.61-0.76, p= < 0.001). Measurement error was large in the IPAQ-SF (-3942 to 4509 metabolic equivalents (METS)-1minute-1week 95% limit of agreement) and the PASE (-130.28 to 112.76 95% limit of agreement). In terms of construct validity, the IPAQ-SF and PASE correlated well with each other (r=0.62, p= < 0.01) and the SF-12 physical component score (PCS), (r=0.30, p= < 0.01 & r=0.39, p= < 0.01 respectively). The implications of this thesis are that adults aged 45 years and over with joint pain are at higher risk of being inactive and that both the IPAQ-SF and PASE are poor in their measurement properties for measuring of PA in this population.
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