Heterogeneity of tibial plateau cartilage in response to a physiological compressive strain rate.

Knowledge of the extent to which tibial plateau cartilage displays non-uniform mechanical topography under physiologically relevant loading conditions is critical to evaluating the role of biomechanics in knee osteoarthritis. Cartilage explants from 21 tibial plateau sites of eight non-osteoarthritic female cadaveric knees (age: 41-54; BMI: 14-20) were tested in unconfined compression at 100% strain/s. The elastic tangent modulus at 10% strain (E(10%) ) was calculated for each site and averaged over four geographic regions: not covered by meniscus (I); covered by meniscus-anterior (II); covered by meniscus-exterior (III); and covered by meniscus-posterior (IV). A repeated-measures mixed model analysis of variance was used to test for effects of plateau, region, and their interaction on E(10%) . Effect sizes were calculated for each region pair. E(10%) was significantly different (p<0.05) for all regional comparisons, except I-II and III-IV. The regional pattern of variation was consistent across individuals. Moderate to strong effect sizes were evident for regional comparisons other than I-II on the lateral side and III-IV on both sides. Healthy tibial cartilage exhibits significant mechanical heterogeneity that manifests in a common regional pattern across individuals. These findings provide a foundation for evaluating the biomechanical mechanisms of knee osteoarthritis.