Evaluation of the Potential Effects of Intra-Articular Rifamycin SV Injection into the Knee Joint on Articular Cartilage and Synovial Membrane

Introduction: Rifamycin is widely used as a broad-spectrum antimicrobial agent; recent studies have demonstrated the anti-inflammatory properties of rifamycin SV. Our study aimed to determine the adverse effects of intra-articular injection of rifamycin SV on the articular cartilage and synovial membrane of the knee joint. Methods: Thirty-two Wistar albino male rats were assigned to experimental and control groups (n=8 per group). On the first day, a single dose of 5mg/kg rifamycin SV (Rif; Koçak Farma, Türkiye) was injected into the right knee of the rats in the experimental groups (E1/E2), and a single dose of 0.9% isotonic sodium solution was injected into the right knee of the rats in the control groups (C1/C2). E1 and C1 rats were euthanized on the 7th day, and E2 and C2 rats were euthanized on the 28th day. Macroscopic and histopathological evaluations of the articular cartilage structures and synovial inflammation were performed. The histopathological grading and staging system of the Osteoarthritis Research Society International was used to evaluate the cartilage structures, with p<0.05 considered statistically significant. Results: There were no statistically significant differences between the E1 and C1 groups or between the E2 and C2 groups in cartilage damage degree, stage, or score on the 7th day (p=0.117, p=0.197, p=0.197) and on the 28th day (p=0.077, p=0.061, p=0.062). When the E1 and C1 groups were examined to determine degrees of synovial inflammation, inflammation was significantly more common in the rifamycin SV (E1) group (p<0.001 on day 7). In contrast, degrees of synovial inflammation did not differ significantly between the E2 and C2 groups (p=0.256, day 28). Conclusion: The intra-articular administration of rifamycin SV did not have a negative effect on articular cartilage but increased synovial inflammation on the 7th day. ©Copyright 2026 by the University of Health Sciences Türkiye, İstanbul Training and Research Hospital/İstanbul Medical Journal published by Galenos Publishing House.