Bone Mass and Sexual Dimorphism in Clarke's Angle: A Multivariate Regression Approach to the Medial Longitudinal Arch...

Background: Flattening of the medial longitudinal arch is traditionally attributed to excess body weight and Body Mass Index (BMI). However, controversy exists regarding whether adiposity or skeletal structure drives this biomechanical alteration, and which podometric index best detects it. Methods: A cross-sectional study evaluated 99 healthy university students (50 males, 49 females). Body composition was assessed via a four-component model. Plantar footprints were captured using 4K digital podoscopy and analyzed with five morphometric indices. Arch predictors were identified using multivariate regression models (Elastic Net regression) and Generalized Additive Models (GAMs). Results: Only Clarke's Angle detected significant sexual dimorphism, showing structurally higher arches in females (50.28° ± 7.14) than in males (41.82° ± 11.20; p < 0.001). Multivariate analysis revealed bone mass as the dominant structural predictor, exerting a non-linear negative association with the arch profile, which stabilizes beyond 12 kg. BMI was not a significant predictor, whereas body fat percentage showed a modest positive association. Conclusions: Plantar arch morphology is strongly associated with skeletal load (anthropometrically estimated bone mass) rather than adiposity or BMI. Within this specific cohort, Clarke's Angle emerged as a highly sensitive instrument for characterizing sexual dimorphism. Clinical assessments diagnosing functional flatfoot should prioritize underlying bone structure over BMI, particularly when evaluating a healthy and physically active university population. Future studies incorporating DXA or radiographic validation are needed to confirm these anthropometric findings.