Moreover, using the combination of MMP-9 and VEGF-C and the cut-offs suggested by the ROC curve analysis, seven out of the eight patients (88%) with samples before and during osteonecrosis were already showing values of MMP-9 and/or VEGF-C below the cut-offs: the combination of these two biomarkers could effectively predict the onset of osteonecrosis; however, these results need to be validated in a larger cohort of patients with multiple data points and long-term follow-up. The gene discussed is MMP9; the disease is osteonecrosis.