Intra-articular steroid injection at the time of knee arthroscopy increases risk of post-operative infection.

PURPOSE To evaluate the risk of post-operative infection after intra-articular steroid injection at the time of knee arthroscopy at a single institution high-volume sports medicine practice. METHODS The electronic medical record at a single institution was queried for all patients who underwent knee arthroscopy from 2011 to 2019. Patients were included if they underwent more simple arthroscopic procedures: diagnostic arthroscopy, meniscectomy, loose body removal, synovectomy, or microfracture. Patients were excluded if they underwent more complex procedures, such as ligament reconstruction, meniscus repair, or any open procedures. These patients' medical records were then queried for current procedural terminology and international classification of disease codes indicating post-operative infection. Individual chart review was performed on this group of patients to determine if a true postoperative infection occurred within 6 months of the index arthroscopy. Patients were then categorized into "intra-operative steroid injection" versus "no steroid" based on each surgeon's preferred intra-operative analgesic injection cocktail. RESULTS A total of 6889 patients were identified, including 2416 (35.1%) who were given intra-articular steroid at the time of knee arthroscopy. Post-operative infection occurred in 10 patients (0.15%) at a median of 18 days (range 9-42 days), 7 who received intra-operative steroid injection (0.29%) and 3 who did not (0.067%), p = 0.040. The relative risk of infection for those who received intra-operative steroid injection was 4.32 times higher than those who did not, with a number needed to harm of 448. There were no significant differences in age, body mass index, smoking status, or the prevalence of diabetes between those who got infected and those who did not. CONCLUSIONS Knee infection following arthroscopic surgery is rare. Intra-operative steroid injection during arthroscopic knee surgery is associated with a 4.3-fold increased risk of subsequent knee infection. While the overall risk remains low, the use of intra-operative steroids is expected to result in one additional knee infection for every 448 arthroscopic procedures performed. LEVEL OF EVIDENCE IV.