Purpose <p>To assess whether diabetes mellitus (type 1 or type 2) increases the risk of developing adhesive capsulitis (frozen shoulder).</p> Methods <p>A systematic review and meta-analysis were conducted in 2026 using multiple electronic databases. Additional studies were identified through screening reference lists and consulting professional networks. Studies examining the relationship between diabetes mellitus and the incidence of adhesive capsulitis were eligible for inclusion. Study quality and bias risk were assessed, and when enough data were available, a random-effects meta-analysis was performed to estimate the general association between diabetes and the development of frozen shoulder.</p> Results <p>The combined analysis showed that people with diabetes had 3.69 times higher odds (95% CI 2.99–4.56) of developing adhesive capsulitis compared to people without diabetes. Several additional risk factors were noted across studies, including poor glycemic control, obesity, hyperlipidaemia, hypertension, thyroid issues, age between 40 and 65, female gender, smoking, and alcohol use.</p> Conclusion <p>Diabetes mellitus is strongly associated with an increased risk of adhesive capsulitis. However, the observed association may be influenced by unmeasured confounding factors. Further high-quality longitudinal studies are required to clarify the causal relationship and underlying mechanisms.</p>