Osteoarthritis (OA) involves pathological changes in all joint tissues, including cartilage degradation and synovitis. Synovial inflammation is significantly associated with pain severity and incidence of OA. Apparently, synovitis also plays an active role in the initiation and progression of cartilage erosion in gonarthrosis by direct secretion of catabolic enzymes as well as factors that stimulate the catabolic activity of chondrocytes. New studies demonstrate the presence of cytokines and chemokines in the articular synovial fluid. Among arthroses, the incidence of knee localized OA is the largest. In early stages, first-line treatment consists of adjusting the lifestyle, weight loss recommendations, symptomatic treatment with non-steroidal anti-inflammatory drugs and intraarticular (IA) administration of corticosteroids (CS). Intra-articular injection therapy with hyaluronic acid (IA HA) is a viable option after using the first-line methods. Efficacy of hyaluronan is debated even 20 years after its implementation on the world market. Recently conducted systematic reviews and metaanalytical studies compare the effectiveness of IA HA injections with placebo treatment. Results advocate for hyaluronic acid. [ABSTRACT FROM AUTHOR]