The incidence of osteoarthritis is increasing to almost epidemic levels due to an aging population in developed countries. Our group is committed to approach osteoarthritis from an O-linked glycobiological angel. By doing this we have developed and adopted tools for O-glycodiscovery and clinical O-glycomics. The O-glycome and O-glycoproteome of synovial fluid from osteoarthritic patient was revealed using MS. Pathological changes, including sulfation pattern of the O-linked glycome was identified. In addition to standard CID, we adopted Ion-Mobility MS (IM-MS) and Selected Reaction Monitoring (SRM) to into identify sites of sulfation of core-1 structures Gal1-3GalNAc with or without sialic acid. This included sulfation of non-reducing terminal galactose and sialic acid as well as reducing terminal GalNAc residues. We then used recombinant expression of glycosyltransferases in CHO-cells to identify glycosyl- and sulfo-transferases responsible for modification of the osteoarthritic glycome. Finally, we demonstrated the power of SRM for screening of patients sample and compared it to a developed lectin-ELISA for OA diagniostics that could be used in clinics.