Aims Knee osteoarthritis (OA) is a common cause of pain and disability in adults. Intra-articular injections are important components in the management of knee OA symptoms, but there are concerns that these injections may be associated with the progression of OA. Therefore, this study determined how the likelihood of progression to arthroplasty is influenced by intra-articular injection of corticosteroid (CS) and/or hyaluronic acid (HA) in patients with knee OA. Methods This population-based cohort study included patients aged 40 to 60 years receiving an initial intra-articular injection of CS and/or HA from 1 January 2000 through 31 December 2010, who resided in Olmsted County, Minnesota, USA. The primary outcome was the likelihood of joint arthroplasty by number of intra-articular injections received evaluated by Cox proportional hazards regression. Results A total of 1,897 patients (n = 2,336 knees) who received 8,600 injections (n = 5,786 CS; n = 2,814 HA) were included (mean age 51.9 years (SD 5.5); 1,515 females (64.9%); mean BMI 34.8 kg/m 2 (SD 8.0)), and 917 (39.3%) subsequently underwent arthroplasty. Accounting for age, BMI, and Kellgren-Lawrence (KL) grade at initial injection, the number of intra-articular injections was associated with an increased likelihood of arthroplasty (hazard ratio (HR) 1.12 (95% CI 1.08 to 1.17)). For patients with early OA (KL grade 0 to 1), CS injections (HR 1.27 (95% CI 1.17 to 1.37)) were associated with an increased likelihood of arthroplasty versus HA (HR 1.12 (95% CI 1.06 to 1.19)). Conclusion Each intra-articular injection was associated with a 12% increased likelihood of arthroplasty. With subgroup analysis, CS injections in early OA were associated with a 27% increased likelihood of arthroplasty. Cite this article: Bone Jt Open 2026;7(11):1462–1470.