Background/Purpose

The factors associated with knee cartilage volume in younger population are insufficiently explored. The aims of this study were to describe the associations between physical activity, physical performance, body composition, inflammatory and hormonal factors and tibial cartilage volume and to explore if these factors explained the sex difference in tibial cartilage volume observed in young adults.

Methods

Subjects broadly representative of the Australian population (n=328, aged 31-41 years, female 48.7%) were selected from the Childhood Determinants of Adult Health study. They underwent T1 and T2 weighted fat- suppressed magnetic resonance imaging (MRI) scans of their knees. Tibial bone area and cartilage volume were measured from MRI. Physical activity (long version of IPAQ questionnaires) and physical performance measures such as long jump, leg muscle strength, and physical work capacity at 170 heartbeats per minute (PWC₁₇₀) were measured. Sex hormone binding globulin (SHGB, females only), testosterone (females only), C-reactive protein and fibrinogen were measured 5 years prior. Fat mass and lean mass were calculated from skinfold.

Results

After adjustment for age, sex, BMI, injury, tibial bone area and duration of follow-up, physical performance measures including PWC₁₇₀ (β: 3.4 mm³, 95% CI: 1.1, 5.8) and long jump (β: 4.3 mm³, 95% CI: 0.5, 8.0) measured 5 years prior were positively associated with tibial cartilage volume. Physical activity measures (hr/week) including total physical activity (β: 18.0 cm³, 95% CI: 7.9, 28.2), vigorous (β: 32.1 mm³, 95% CI: 7.9, 56.4), moderate (β: 20.6 mm³, 95% CI: 0.8, 40.3) and walking (β: 23.7 mm³, 95% CI: 4.4, 43.1) measured 5 years prior were positively associated with tibial cartilage volume. The associations of physical activity were independent of fitness levels and current physical activity level.

Lean body mass (β: 26.4 mm³, 95% CI: 13.6, 39.1) was positively and fat mass (β: -11.8 mm³, 95% CI: -22.2, -1.4) was negatively associated with cartilage volume. Fibrinogen was negatively associated with the cartilage volume (β: -0.15 mm³, 95% CI: -0.28, -0.018). SHBG in females was positively (β: 0.67 mm³, 95% CI: 0.14, 1.2) and free androgen index in females was negatively associated with tibial cartilage volume.

Males had greater tibial cartilage volume than females in adjusted analysis. The magnitude of this association (β of adjusted analysis) decreased by 54%, 47%, 42%, 37%, and 24% after further adjustment for lean body mass, leg strength, fat mass, PWC₁₇₀and fibrinogen, respectively, but remained largely unchanged after adjustment for other factors.

Conclusion

Lean mass, physical activity and physical performance measures are beneficially, while obesity measures and fibrinogen are negatively associated with tibial cartilage volume in young adulthood. The sex difference in tibial cartilage volume is largely explained by variations in body composition and physical performance measures. Physical activity measured 5 years prior was independent of the fitness and current physical activity levels, suggesting cartilage development in younger life can be modified by environmental intervention.

ACR Meeting Abstracts - https://acrabstracts.org/abstract/physical-performance-and-obesity-measures-are-associated-with-tibial-cartilage-volume-and-explains-the-sex-difference-in-cartilage-volume/