Musculoskeletal conditions are prevalent worldwide and are associated with pain, disability and impaired quality of life (QoL). Osteoarthritis (OA) is a common, costly and disabling musculoskeletal condition. Lower limb OA research has focussed on the hip and knee and, as a consequence, impairments characterising ankle OA are not well understood.This thesis aims to advance our understanding of the physical, functional and psychological impairments and associated disability in individuals with persistent ankle symptoms and in those with radiographic evidence of ankle OA. Study 1: A systematic literature review and meta-analysis was conducted to synthesise and appraise the quality of studies investigating physical impairments in ankle OA. The review identified eight studies, three of which were included in the meta-analyses. Meta-analyses revealed large impairments of ankle sagittal plane range of motion (ROM) on the affected compared to the unaffected side and less sagittal plane torque in ankle OA compared to controls. Evidence from single studies indicated deficits in frontal plane ROM and strength, talar translation and rotation, balance, electromyography of ankle muscles, abnormal bony alignments and greater fatty infiltrate in all calf muscle compartments in individuals with ankle OA. Critical appraisal of the literature revealed limitations surrounding assessor blinding, measurement validity, and lack of generalization. Study 2: A cross-sectional laboratory study of 96 participants compared physical measures of function, strength, ROM and posture and patient-reported outcomes in 1) individuals with symptoms and radiographic evidence of ankle OA to asymptomatic individuals; and 2) asymptomatic individuals with and without radiographic evidence of ankle OA. Those with symptomatic OA reported greater pain, disability, instability, kinesiophobia, lower function and QoL, and exhibited significant deficits in muscle strength, ROM and ambulatory function compared to asymptomatic individuals. Most patient-reported and physical outcomes were similar between asymptomatic individuals with and without radiographic OA. Stair function times were significantly associated with QoL and self-reported function. ii Study 3: A cross-sectional exploratory survey (n=394) was conducted to compare selfreported daily living and sports function, ankle pain and disability, physical activity, ankle instability, and QoL between individuals with and without persistent ankle pain and stiffness, and to explore factors associated with QoL. Individuals with ankle symptoms reported worse scores for all measures, except self-reported physical activity. Daily living function and age explained 66% of the variance in QoL. Study 4: Individuals with and without persistent ankle pain and stiffness (n= 231) participated in an online survey to obtain data about pain severity, pain self-efficacy, anxiety, depression, kinesiophobia, pain catastrophizing, and function. Individuals with persistent ankle pain reported higher pain and depressive symptoms, an...