CHI3L1 and osteoarthritis: The aberrant and elevated expression of YKL-40 is largely associated with the pathogenesis of a variety of human diseases, such as rheumatoid- and osteoarthritis, hepatic fibrosis and asthma, which is connected to its pathological function and is associated with extracellular matrix remodeling, suggesting that the serum levels of YKL-40 serve as a diagnostic and prognostic biomarker [7].