Body mass index and the anterior cruciate ligament - integrating mechanical and inflammatory mechanisms

Introduction. Obesity is a chronic metabolic disorder characterised by excess adiposity, persistent low-grade inflammation, and high frequency of musculoskeletal complications in both athletic and non-athletic populations. Body mass index and fat distribution, particularly visceral adiposity, are key determinants of metabolic and orthopaedic risk, including disorders of the knee tendons and ligaments. From adiposity to ligament pathology. In obesity, white adipose tissue undergoes phenotypic remodelling toward a pro-inflammatory state, marked by immune cell infiltration, increased secretion of cytokines and adipokines, and reduced adiponectin levels. These alternations promote lipotoxicity and ectopic fat deposition in skeletal muscle, ligaments, fat pads, and entheses, contributing to sarcopenic obesity, angiofibroblastic degeneration, and impaired ligament healing. Clinical implications. Elevated body mass index increases mechanical loading and alters lower-limb biomechanics, thereby promoting repetitive microtrauma, chronic inflammation, and higher incidence of tendinopathies, particularly of the extensor mechanism and pes anserinus. In individuals with body mass index above 25 kg/ m^2, published studies report a higher prevalence of multiligament knee injuries, a greater proportion of trauma-related anterior cruciate ligament ruptures, increased postoperative complications, and delayed functional recovery. However, heterogeneity in study design limits precise quantification of effect sizes. Conclusion. Excess adiposity likely increases anterior cruciate ligament injury risk through the combined effects of mechanical overload and obesity-related inflammation and is associated with more extensive ligament damage and a less favourable postoperative course. Integrated interventions targeting fat-mass reduction, metabolic optimisation, and neuromuscular conditioning may enhance recovery, reduce re-injury risk, and support long-term knee joint health. This conceptual framework is applicable across age groups in both recreational and competitive sports populations.