MMP9 and osteonecrosis: Decreased levels of MMP-9 were also observed in patients with incident osteonecrosis (median 38,711 pg/mL [IQR 24,822 to 72,420]) compared with patients free from osteonecrosis (median 121,223 pg/mL [IQR 68,135.5 to 195,583.5]) and those with historical osteonecrosis (median 126,312 pg/mL [IQR 58,997–165,988.3], p = 0.001, Figure 3c).