Potential Associations Between Metabolic Syndrome and Shoulder Disorders: Insights Into Rotator Cuff Tears and Frozen Shoulder

Metabolic syndrome and its components are strongly associated with shoulder pathologies, including rotator cuff tears (RCTs) and frozen shoulder (FS). For atraumatic posterosuperior RCTs, key risk factors include a critical shoulder angle (CSA) ≥35°, diabetes, BMI, hypo-high-density lipoproteinemia (hypo-HDLemia), and metabolic syndrome, which is also linked to bilaterality. Elevated serum fasting glucose levels, even within normal ranges, and increased insulin resistance contribute to the risk of RCTs, while hypo-HDLemia is associated with larger tear sizes and higher retear rates in massive RCTs. Reconstituted high-density lipoprotein offers protective and regenerative benefits to rotator cuff fibroblasts under hypoxic conditions, suggesting its potential for therapeutic tendon repair. For FS, altered serum lipid profiles, high serum glucose levels, elevated high-sensitivity C-reactive protein levels, and subclinical hypothyroidism are strongly associated with its pathogenesis, highlighting the interplay between metabolic and inflammatory factors. Therefore, metabolic syndrome and its constituents significantly contribute to shoulder disorders, and controlling these factors may help prevent their development and progression. These findings underscore the importance of early metabolic screening and targeted interventions to reduce the burden of shoulder pathologies, while further research is needed to clarify the underlying mechanisms and refine treatment strategies.