Background: Corticosteroids are commonly used for intra-articular (IA) treatment of osteoarthritis (OA) in horses; however, there is controversy regarding its use as a multiple-injection treatment and for the appropriate dosing. Objectives: This systematic review collected and critically appraised the current evidence regarding the effects of multiple injections and various doses of corticosteroids for treating osteoarthritis. Study design: Systematic review. Methods: Titles of published articles up to June/2022 generated by searches in PubMed, CAB, and the Web of Science were screened using general inclusion criteria. Each question for corticosteroid effects (multiple treatments and different doses) had further inclusion requirements. The risk of bias was assessed according to the study design. Results: Of 6,417 titles generated by the systematic search, only nine met all inclusion criteria for multiple-injection treatments, and 14 were included for screening the effects of various doses. Most studies showed unclear/high risk of bias. Multiple-injection protocols showed better symptom-modifying changes at first injections with decreased improvements. Disease-modifying changes improved over shorter follow-ups; however, degenerative changes were seen in the longer term. Determining the dose effect of corticosteroids was challenging regarding different doses because there were few in vivo studies. In vitro, lower doses appeared to be safer for articular tissues. Main limitations: Lack of studies regarding the topics. Conclusions: No benefits but drawbacks of multiple IA injections in the long term were found in this review, and results regarding the dose of corticosteroids in OA joints were not consistent in in vivo, but in vitro, studies pointed out that lower doses might be safer for joint tissues.

Background: The importance of intra-articular corticosteroid treatment for osteoarthritis with its possible adverse effects requires a comprehensive review. Objectives: This review answers the following questions: 1) What evidence is available regarding the symptom-modifying and disease-modifying changes related to a single intra-articular corticosteroid injection for treating osteoarthritis? Moreover, 2) What evidence suggests corticosteroids are detrimental to equine joint health? Study design: Systematic review. Methods: A systematic search was conducted in June/2022 in PubMed, CAB, and the Web of Science. Inclusion criteria were applied to titles and abstracts. For each question, further criteria were applied. The risk of bias was assessed according to the study design. Results: We generated 6,417 titles, and 23 articles fit all inclusion criteria for single-injection corticosteroid treatments; 21 were included regarding corticosteroid effects on joint health. Studies were usually rated as having an unclear risk of bias. Single-injection protocols lead to short-term symptom-modifying osteoarthritic changes with conflicting results regarding disease-modifying osteoarthritis. Healthy joints demonstrated disturbances in metabolism and tissue changes, with dose-dependent effects found in vitro. Main limitations: There is a lack of studies regarding the topics–primarily for equine species. Conclusions: Symptom-modifying osteoarthritic changes after a single injection are short-term; however, a consistent disease-modifying osteoarthritis effect is yet to be established. Joint health appears to be disturbed by corticosteroids as their effects on normal joints show adverse changes in tissues and metabolism.