Introduction <p>Intra-articular steroid injections (IASI) and knee arthroscopies are occasionally performed after total knee arthroplasty (TKA) in patients with persistent pain, inflammation, or mechanical symptoms. Prior studies have raised concern regarding a potential increased risk of periprosthetic joint infection (PJI) following such procedures. Comparative data on infection rates across these post-TKA interventions remain limited. This study evaluates and compares the incidence of PJI in patients who underwent IASI, knee arthroscopy, or both following primary TKA.</p> Materials and methods <p>A retrospective cohort study was conducted using patients who received primary TKA between January 2017 and January 2023. PJI was defined according to the 2018 Musculoskeletal Infection Society (MSIS) criteria. Infection rates were compared using Fisher’s exact test. The control group was propensity score matched on a 5:1 ratio independently for IASI and knee arthroscopy based on age, sex, ASA score, Charlson comorbidity index, and surgical date.</p> Results <p>362 patients (372 knees) met inclusion criteria for the treatment groups: 173 received steroid injection only (group 1), 142 underwent arthroscopy only (group 2), and 57 received both (group 3). When comparing all treatment groups (1.34%) to the matched control group of 1850 patients (0.97%), there was no significant difference between infection rates (<i>p</i> = 0.5708) at a minimum 2 year follow up. The infection rate in group 1 was 1.73%, in group 2 was 0.70%, and in group 3 was 1.75%. Two of the 3 infections in group 1 occurred within 30 days of IASI. The 6 month PJI rate in the 230 knees receiving IASI (group 1 and 3) was 0.87%.</p> Conclusions <p>The fact that two infections occurred within 30 days of IASI suggests a slightly increased risk of infection after IASI. However, reported PJI rates within 6 months of IASI and Arthroscopy are very low and both are considered reasonable treatment options in selected patients.</p>