Background <p>Sarcopenia, the progressive loss of muscle mass and function, is increasingly recognized in chronic inflammatory diseases. Beyond joint damage, Spondyloarthritis leads to reduced mobility, decreased physical activity, and systemic inflammation, which may accelerate sarcopenia. This study evaluated sarcopenia in patients with spondyloarthritis, including ankylosing spondylitis (AS) and psoriatic arthritis (PsA), using muscle mass index (MMI) and correlated it with disease parameters.</p> Method <p>Fifty AS patients and 50 age- and sex-matched healthy controls were enrolled. Patients underwent a clinical examination and assessment of disease activity and functional status. Lee’s equation was used to estimate muscle mass, and muscle mass index (MMI) was calculated.</p> Results <p>Muscle Mass and MMI were significantly lower in patients (PsA and AS groups) compared to controls (<i>p</i> = 0.006 and <i>p</i> = 0.003, respectively). Sarcopenia was more prevalent in the patient group (68%) than in controls (36%) (<i>p</i> = 0.001). Grade 2 sarcopenia was more dominant in PsA and AS patients than in controls (<i>p</i> = 0.000). Logistic Regression in PsA showed that low muscle mass (≤ 23.66 kg) and elevated ESR (&gt; 19.8 mm/hr) were significant independent predictors of sarcopenia in PsA patients (Muscle mass: OR = 14.2, <i>p</i> = 0.031), (ESR: OR = 12.0, <i>p</i> = 0.043).</p> Conclusion <p>Sarcopenia is common in Spondyloarthritis and is associated with functional impairment and disease burden. Early screening and interventions are essential to mitigate long-term disability.</p>