This paper enhances the understanding and measurement of Healthy Ageing (HA) through a systematic review of its multidimensional operationalisation. Despite progress in HA research, no consensus exists on its constitutive elements, and current frameworks often do not capture its full complexity. Building on the World Health Organization (WHO) HA definition, we organise empirical evidence under three dimensions: intrinsic capacity (IC), functional ability (FA) and the environment (ENV). To identify conceptual, empirical and methodological gaps, we provide a structured synthesis of concepts, measures and instruments used in HA research, evaluating methodological advancement and standardisation in HA measurement. Following PRISMA guidelines, we extract data from 55 quantitative, qualitative and mixed-methods studies with a multidimensional HA focus. We arrange evidence into three primary domains (IC, FA and ENV; first order), 15 sub-domains (second order) and 84 themes (third order). We identify operational categories via thematic analysis and inductively determine the final categorisation, moving from third to first order based on conceptual and measurement considerations. Given the lack of systematic knowledge on ENV, we generate a more nuanced categorisation capturing different levels of analysis and contexts. We compute a mean usage ratio to assess differences in the application of validated tools across HA aspects. The review revealed substantial variability in HA conceptualisation and measurement. IC and FA are the most extensively studied domains, with well-established measurement approaches and widespread use. Common themes include locomotion, cognitive capacities and functional status. ENV remains significantly underexplored and lacks standardised measurement, as mainstream assessments still prioritise deficit-based approaches over enabling environments. This analysis calls for a standardised, multidimensional HA model integrating individual and contextual factors, recognising the role of structural environmental supports in shaping ageing trajectories. Future research should prioritise comprehensive HA measurement and pursue an interdisciplinary approach bridging conceptual and methodological gaps to inform HA policies effectively.