MAPK8 and disease of the tendon: ROS, related to the increased expression of matrix metalloproteinases (Wunderli et al., 2020), activate several pathways, including the c-Jun N-terminal kinase (JNK) (Wang et al., 2007) and NF-κB pathways (Best et al., 2020); however, further studies are required to elucidate the manner in which oxidative stress leads to tendinopathy.