The crossroads between osteosarcopenia and intrinsic capacity-a narrative review

Intrinsic capacity (IC) is defined as the composite of physical and mental abilities an individual possesses, encompassing 5 domains: cognition, psychological health, sensory function, vitality, and locomotion. This construct is central to the World Health Organization's framework for assessing functional ability in older adults. Growing evidence highlights the critical role of the musculoskeletal system in maintaining these domains, while conditions such as sarcopenia, osteoporosis, and their coexistence as osteosarcopenia (OS) are increasingly associated with IC decline. This narrative review compiles current evidence on the modulatory role of muscles and bones in IC and the impacts of sarcopenia, osteoporosis, and OS. Most findings suggest that musculoskeletal tissues influence IC not only through biomechanical functions but also as secretory organs, releasing myokines and osteokines with endocrine, paracrine, and autocrine effects. Among the most studied are brain-derived neurotrophic factor, irisin, osteocalcin, and interleukin-6. Dysregulation of these pathways, along with biomechanical dysfunction and systemic inflammation, links sarcopenia, osteoporosis, and OS to IC impairment. Further research is needed to clarify the specific mechanisms involved, particularly in the sensory and vitality domains, to inform targeted interventions that promote healthy aging.