Haematogenous models of septic arthritis have some inherent disadvantages, such as the manifestation of arthritis relies on chance, the size of the inoculum is unknown and the number of animals to be studied cannot be reduced because the animals cannot serve as their own controls. This study aimed to develop a rat model of knee septic arthritis by injecting a known inoculum of Staphylococcus aureus into the joint. The left knees of 27 Sprague Dawley rats were injected with four different inoculum concentrations of a sensitive strain of S. aureus (30,000 colony-forming units (CFUs), n = 3; 18,550 CFUs, n = 6; 15,500 CFUs, n = 9; and 7700 CFUs, n = 9); the right knees served as controls. Clinical, microbiological and histological variables were assessed two and seven days later. The main criterion for diagnosing septic arthritis was a positive culture of synovial fluid. The rate of microbiologically confirmed septic arthritis was high for all inoculum concentrations (3/3, 6/6, 8/9 and 7/9, respectively), and the rate of bacteraemia was also high. Animal welfare was better for the two lowest inoculum concentrations. No animal reached the pre-established humane end points. Overall, the third inoculum was considered the most suitable. Thus, acute septic arthritis can be caused in rats by inoculating 15,000 CFUs of an ATCC strain of S. aureus directly into the knee joint. Overall, the model seems to be useful for studying the effectiveness of drugs for the treatment of acute septic arthritis.

化脓性关节炎的血源性模型具有一些固有的缺点，例如关节炎的表现依赖于偶然性，接种物的大小是未知的，并且由于动物不能作为自己的对照而不能减少要研究的动物数量。本研究旨在通过将已知的金黄色葡萄球菌接种物注射到关节中来开发膝关节脓毒性关节炎的大鼠模型。向 27 只 Sprague Dawley 大鼠的左膝注射了四种不同浓度的金黄色葡萄球菌敏感菌株（30,000 菌落形成单位 (CFU)，n  = 3；18,550 CFU，n  = 6；15,500 CFU，n  = 9 ; 和 7700 CFU，n = 9); 右膝作为对照。两天和 7 天后评估临床、微生物和组织学变量。诊断化脓性关节炎的主要标准是滑液培养阳性。对于所有接种浓度（分别为 3/3、6/6、8/9 和 7/9），微生物学证实的化脓性关节炎的发生率都很高，而且菌血症的发生率也很高。两种最低接种浓度的动物福利更好。没有动物达到预先确定的人道终点。总的来说，第三种接种物被认为是最合适的。因此，可以通过接种 15,000 CFU 的金黄色葡萄球菌ATCC 菌株在大鼠中引起急性化脓性关节炎直接进入膝关节。总体而言，该模型似乎有助于研究药物治疗急性化脓性关节炎的有效性。