Background/Purpose: Physical activity interventions are often advised for management of osteoarthritis patients, despite contradictory findings regarding its effect on knee structure. In particular, there is little evidence relating childhood physical performance measures to adult joint structure. The aim of this cohort study was to determine the associations between childhood physical performance measures and knee cartilage volume and tibial bone area in adults 25 years later.

Methods: Subjects broadly representative of the Australian population (n=298, aged 31-41 years, female 48.7%) were selected from the Childhood Determinants of Adult Health study. They underwent T1-weighted fat- supressed magnetic resonance imaging of their dominant knee and cartilage volume and tibial bone area were measured. Childhood measures including physical work capacity at 170 beats per minute (PWC₁₇₀), leg and hand muscle strength, sit-ups, long-run, and short-run were measured by standard protocols 25 years prior.

Results: There were consistent and significant associations of all childhood measures including PWC₁₇₀ (β: 0.48 cm² per 100 mW, 95% CI: 0.22, 0.73), hand muscle strength (β: 1.49 cm² per 100g, 95% CI: 0.79, 2.19), leg muscle strength (β: 0.29 cm² per 100g, 95% CI: 0.09, 0.50), short-run (β: -0.71 cm² per second, 95% CI: -1.21, -0.21) and sit-ups (β: 0.28 cm² per count/10, 95% CI: 0.13, 0.43) with adult tibial bone area in multivariable linear regression, after adjustment for sex, childhood age, duration of follow-up and childhood and adulthood measures (body mass index and knee injury). In addition, these associations were independent of the corresponding adulthood fitness measures and tibial cartilage volume_.

Similarly, there was a significant positive association between childhood PWC₁₇₀ and adult medial tibial cartilage volume (β: 0.1 mm³ per 100 mW, 95% CI: 0.03, 0.17) after adjustment for covariates including adult PWC₁₇₀. The magnitude of the association decreased by 33% but remained significant after further adjustment for tibial bone area. Other childhood measures such as hand muscle strength (β: 0.21 mm³ per 100g, 95% CI: 0.04, 0.37) and sit-ups (β: 0.04 mm³ per count/10, 95% CI: 0.01, 0.08) were significantly associated with medial tibial cartilage volume, but these became non-significant after further adjustment for medial tibial bone area.

Conclusion: A number of childhood physical performance measures are significantly associated with knee bone area and cartilage volume in adulthood. The associations with cartilage volume appear to be mediated by tibial bone area. This suggests physical activity in childhood can independently influence adult knee joint health possibly through adaptive mechanisms during growth.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/childhood-physical-fitness-predicts-adulthood-knee-cartilage-volume-and-bone-area-a-25-year-cohort-study/