Osteoarthritis is the commonest joint disease worldwide; in a relatively short period of time, it can result in permanent loss of working capacity and even to disability. Changes in the joint structure of patients with osteoarthritis (OA) may depend on the basic therapy they receive, and the control of osteoarthritis. The purpose of this work is to prove the value of elastometry in assessing the severity of synovitis in the knee joints of patients with osteoarthritis, depending on the basic therapy they receive and the control of osteoarthritis. The initial level of stiffness of the synovial membrane in all groups demonstrated no significant differences and was 8.59±0.97 kPa for the first group, 9.97±1.15 kPa for the second group, and 9.11±0.69 kPa for the third group. Correlation analysis at the time of inclusion in the study showed a close relationship in all groups of patients between the stiffness indicators of the synovial membrane in the knee joint, the level of C-reactive protein (r= 0.71, p=0.011) and the level of ESR (r= 0.69, p =0.018, which remained even after 6-month therapy (r= 0.73, p=0.045) and (r=0.69, p=0.021), respectively. Correlation analysis between the level of stiffness and stiffness indicators of the synovial membrane in the knee joint ( r=0.71, p=0.015), the severity of pain in the knee joint according to the Visual Analogue Scale, and the stiffness indicators of the synovial membrane of the knee joint (r= 0.63, p=0.012) at the moment of the inclusion in the study indicates a correlation between stiffness in the synovial membrane and clinical manifestations, which persisted even after 6-month therapy (r= 0.41, p= 0.022) and (r= 0.51, p=0.014), respectively. The results obtained prove the effectiveness of using stiffness assessment of the synovial membrane in the knee joints (elastometry indicators) to evaluate the effectiveness of the basic therapy of patients with osteoarthritis.