We aimed to determine the minimum mechanical impact to cause microstructural damage in the network of collagen (microcracking) within human cartilage and hypothesized that energies below 0.1 J or 1 mJ/mm
We completed 108 low-energy impact tests (0.05, 0.07, or 0.09 J; 0.75 or 1.0 m/s
No specimens presented visible damage following impact. We found that impact energy/energy dissipation density and nominal stress/stress rate were significant (P < 0.05) predictors of microcracking while both strain and strain rate were not. In our test configuration, an impact energy density of 2.93 mJ/mm
An impact energy density of 1.0 mJ/mm