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.