Association of Body Composition and Hormonal and Inflammatory Factors With Tibial Cartilage Volume and Sex Difference in Cartilage Volume in Young Adults.

OBJECTIVE: To describe the associations between body composition and hormonal and inflammatory factors measured 5 years prior and tibial cartilage volume in young adults, and to explore if these factors contribute to the sex difference in tibial cartilage volume.

METHODS: Subjects broadly representative of the young adult Australian population (n = 328, ages 31-41 years, 47.3% women) were selected. They underwent T1-weighted fat-suppressed magnetic resonance imaging (MRI) of their knees. Tibial cartilage volume was measured from MRI. Sex hormone binding globulin (SHBG) and testosterone in a subset of women and C-reactive protein (CRP) level and fibrinogen in both sexes were measured 5 years prior. Body mass index (BMI), fat mass, and lean mass were calculated from height, weight, and skinfolds.

RESULTS: In multivariable analyses, correlates of tibial cartilage volume included lean body mass (β = 26.4 mm(3) ; 95% confidence interval [95% CI] 13.6, 39.1), fat mass (β = -11.8 mm(3) ; 95% CI -22.2, -1.4), and fibrinogen (β = -146.4 mm(3) ; 95% CI -276.4, -16.4), but not BMI, testosterone, or CRP level. In women, SHBG was positively associated with tibial cartilage volume (β = 0.67 mm(3) ; 95% CI 0.14, 1.20) and Free Androgen Index was negatively associated with lateral tibial cartilage volume (β = -0.04 mm(3) ; 95% CI -0.07, 0.00). Men had 13% more tibial cartilage volume (500 mm(3) ) than women. The magnitude of this association decreased by 38%, 20%, and 37% after adjustment for lean body mass, fat mass, and fibrinogen, respectively.

CONCLUSION: Body composition, sex hormones, and fibrinogen correlate with knee cartilage volume in young adult life. Sex difference in knee cartilage volume is contributed largely by variations in body composition and/or fibrinogen.