Infectious arthritis was modeled on white male Wistar rats by injecting a suspension of Staphylococcus aureus microorganisms into the knee joint of animals, and the effects of the synthetic hormone flosteron were also studied. At the same time, the content of acute-phase proteins (ceruloplasmin, haptoglobin, C-reactive protein (CRP)) and procalcitonin (PCT) as markers of the development of the inflammatory process and bacterial infection was studied in the blood serum of rats. Determination of the content of haptoglobin, ceruloplasmin and CRP was carried out on a Cobas 311 biochemical analyzer, the PCT concentration on a Cobas 411 analyzer using Roche Diagnostics test systems. Analysis of the results showed that when flosteron was administered, the concentration of CRP increased by 1.7 times already on the 3rd day, and by more than 4 times on the 14th day. The content of ceruloplasmin and haptoglobin also increased. The PCT concentration was at the level of the control values. Under the conditions of modeling infectious arthritis, changes in the content of acutephase proteins were observed. The greatest deviations from the reference values were found on the 14th day in animals that were injected with the hormone and S. aureus: the concentration of both CRP, the most objective biochemical marker of the inflammatory process, and PCT exceeded the physiological norm 12 times and more than 7 times, respectively. This indicates that the hormonal drug enhances the inflammatory process, which is confirmed by data that reflect changes in the content of acute-phase proteins. It can be assumed that the use of hormonal drugs contributes to the development of postoperative complications.