RESEARCH ARTICLE Aging is associated with in u

age [4]. The most common pathology observed during sur-gery for chronic painful Achilles tendon is degeneration or components in aging tendons [8]. It appears that both insufficient synthesis and increased degradation of ECM Yu et al. BMC Musculoskeletal Disorders 2013, 14:2 http://www.biomedcentral.com/1471-2474/14/223 and MMP-25, and decreased levels of expression of3College of Medicine, Change Gung University, Kwei-Shan Tao-Yuan, Taiwan Full list of author information is available at the end of the articletendinosis [2]. In addition, most pathological changes in spontaneously ruptured tendons are degenerative [4]. Little is known about the roles of mechanisms respon-sible for aging in the degeneration of tendons, but might contribute to the mechanical deterioration of tendons. The degree of ECM breakdown is controlled by the release of matrix metalloproteinases (MMPs) and their inhibition by tissue inhibitor of metalloproteinases (TIMPs) [9]. Several MMPs have been implicated in chronic tendon pathologies, with increased levels of ex