Synovial fluid from osteoarthritis (OA, n ​= ​25) and knee-injury (n ​= ​13) patients, a synovial fluid pool (SF-control) and purified aggrecan, were chondroitinase digested and together with CS- and HA-standards fluorophore labelled prior to quantitative HPLC analysis. Here, ACAN is linked to osteoarthritis.