Intra-articular tibiofemoral injection of a nonsteroidal anti-inflammatory drug has no detrimental effects on joint mechanics in a rat model.

Administration of intra-articular medications, including corticosteroids and analgesics, is common clinical practice for knee pathology and dysfunction. Non-steroidal anti-inflammatory drugs (NSAIDs) are another category of medication commonly prescribed for their analgesic and anti-inflammatory properties. Recent studies demonstrated the efficacy of injectable NSAIDs in the treatment of intra-articular pathology and postoperative analgesia. However, little data exist regarding the safety of intra-articular injection, despite the increase in its application. Therefore, we investigated the effects of intra-articular NSAID injection on articular cartilage, the anterior cruciate ligament (ACL), and joint function in the rat. Sixty-four Sprague-Dawley rats were divided into either saline (SAL) or ketorolac (NSAID) tibiofemoral single injection treatment groups. Animals were euthanized at 2, 7, 28, and 84 days post-injection for histological and mechanical analyses. Additionally, a subset of animals underwent longitudinal ambulatory evaluation to determine joint functional properties. We hypothesized that intra-articular ketorolac injection would result in no detrimental mechanical, histological, or functional changes. No differences were reported between the NSAID and SAL groups in any of the parameters measured at any time point, demonstrating the potential safety of intra-articular NSAID administration. Therefore, NSAID injection could be further considered for clinical application in humans.