Sarcopenia in rheumatic and musculoskeletal diseases: pathophysiology, diagnosis, and management.

Sarcopenia, defined by the progressive decline of skeletal muscle mass, strength, and performance, is an important, yet often overlooked complication of rheumatic and musculoskeletal diseases (RMDs). It arises from a multifactorial interplay of chronic systemic inflammation, oxidative stress, hormonal dysregulation, mitochondrial dysfunction, and prolonged glucocorticoid therapy. Elevated pro-inflammatory cytokines, such as IL-6, TNF-α, and IL-1β, promote catabolic pathways, impair regeneration, and accelerate muscle degradation. The prevalence of sarcopenia in RMDs may reach 40%, particularly among patients with rheumatoid arthritis, osteoarthritis, and spondyloarthritis. Clinically, it contributes to frailty, disability, increased risk of falls and fractures, and higher mortality. Diagnostic assessment combines muscle strength and performance testing with imaging modalities, including DXA, CT, and ultrasound. Evidence supports multimodal interventions, integrating progressive resistance training, adequate protein intake (1.2–1.5 g/kg/day), and supplementation with branched-chain amino acids, calcium, and vitamin D. Anti-inflammatory agents such as biologic DMARDs may counteract muscle loss while chronic corticosteroid use exacerbates it. Early recognition and multidisciplinary management are essential to preserve muscle function, improve quality of life, and reduce long-term morbidity in patients with RMD-associated sarcopenia.