OBJECTIVE Determining the activity of lysosomal exoglycosidases in tissue cultures of synoviocytes derived from the knee joints of patients with injured anterior cruciate ligaments (ACL), juvenile idiopathic arthritis (JIA), and rheumatoid arthritis (RA). METHODS The following exoglycosidases in cultured synoviocytes were analyzed with p-nitrophenyl derivatives of appropriate sugars as substrates: hexosaminidase (HEX) and its isoenzyme A (HEX-A), beta-glucuronidase (GluA), beta-galactosidase (GAL), alpha-mannosidase (MAN), and alpha-fucosidase (FUC). RESULTS In our cell cultures, fibroblast-like synovial cells (FLS) dominated. In the group of patients with ACL-injuries, and in the groups of patients with JIA and RA, the activity of the investigated exoglycosidases was significantly higher in the intra- rather than in the extracellular compartment. Hexosaminidase was the predominant exoglycosidase. Stimulation of synoviocytes by IL-1beta in cell cultures significantly increased the activity of HEX, HEX-A, and GluA in both compartments, as well as of GAL, MAN, and FUC in the intracellular compartment. Stimulation by IL-1beta rheumatoidal synoviocytes increased by 128-201% the activity of HEX and HEX A in intracellular compartments and 33-72% in extracellular compartment. CONCLUSIONS The profile of lysosomal exoglycosidases in a cell culture of human synoviocytes is similar, but not identical, to those in the knee joint. Hexosaminidase is the dominant glycosidase in cultured unstimulated and IL-1beta-stimulated human synoviocytes. The HEX inhibitors may be new drugs for the treatment of inflamed knee joints.