*2.9. Statistical Methods*

The statistical analyses of IKDC scores and VAS scores were performed using *t*-test and Wilcoxon signed-rank test, respectively. A two-tailed paired *t*-test was used to test the difference of IKDC scores at different time points (before and after the operation) of the same treatment group. To compare the efficacy of treatments, we used a one-tailed *t*-test to test the null hypothesis: IKDC scores of microfracture treatment were higher than that of Kartigen® implantation. The statistical significance of the *t*-tests was set as *p* < 0.05. All statistical analyses were performed using Microsoft Excel.
