Objective <p>Transforaminal epidural steroid injection (TFESI) is highly effective in alleviating radicular back pain. While predictive factors for TFESI treatment outcomes have been previously studied, there is a lack of data on the relationship between facet joint degeneration and TFESI efficacy. This study is aimed at studying the impact of facet joint degeneration on TFESI treatment outcomes for unilateral radicular pain.</p> Design <p>A retrospective analysis was conducted on patients with unilateral radicular pain who underwent lumbosacral TFESI. Pain severity was assessed using the Numerical Rating Scale (NRS) at baseline, 1&#xa0;h post-procedure, and 3&#xa0;weeks post-procedure. Degree of facet joint degeneration was evaluated via MRI. Patients were categorized into two groups: low-grade facet joint degeneration group (group 1) and high-grade facet joint degeneration group (group 2).</p> Results <p>A total of 147 patients were included in the study. NRS scores were significantly higher in group 2 compared to group 1 at the 3rd week follow-up. Treatment success, defined as a ≥ 50% reduction in NRS scores, was also significantly higher in group 1.</p> Conclusion <p>Facet joint degeneration adversely impacts the treatment success of TFESI. A comprehensive evaluation of facet joint pathologies prior to procedure planning is imperative for optimizing treatment outcomes.</p>