“…MMPs take part in degrading aggrecan, which is a typical hallmark of OA [116]. The family comprises 23 enzymes in humans [117] and their increased levels were identified in both the blood and SF of OA patients [118][119][120][121]. Based on their structure and substrate specificity, the family is divided into several subgroups, including typical proteinases (e.g., MMP-1,-9,-13), gelatinases (MMP-2, MMP-9), matrilysins (MMP-7, -16) and those that are membrane bound (e.g., MMP-14, -15, -17), among others [122].…”