A rare complication of septic arthritis following Genicular Nerve Block and Prolotherapy procedure.

Abstract Background: Knee osteoarthritis (OA) is a common source of chronic pain and functional limitation. Non-surgical interventions, including genicular nerve block (GNB) and intra-articular prolotherapy, are increasingly utilized for symptom relief. Although generally safe, serious complications are rare and underreported. Case Presentation: We describe a 72-year-old man with bilateral knee OA who underwent GNB and intra-articular prolotherapy due to inadequate pain control and reluctance for surgery. Procedures were performed under aseptic conditions, with initial symptomatic improvement. Three weeks later, he developed severe left knee pain, swelling, and restricted mobility. Laboratory studies revealed leukocytosis and elevated C-reactive protein. Ultrasound confirmed a large suprapatellar effusion. Synovial fluid and blood cultures grew methicillin-resistant Staphylococcus aureus (MRSA), establishing the diagnosis of septic arthritis. The patient underwent left knee arthrotomy washout and was treated with six weeks of intravenous vancomycin due to intolerance to oral antibiotics. Follow-up demonstrated resolution of infection, normalization of inflammatory markers, and restored knee function. Discussion: Septic arthritis following combined GNB and prolotherapy is exceedingly rare. Potential mechanisms include direct bacterial inoculation during injection or a local environment favorable for bacterial growth induced by prolotherapy. This case highlights the importance of strict aseptic technique, careful patient counseling regarding infection risk, and vigilance for early signs of joint infection. Conclusion: While GNB and intra-articular prolotherapy remain effective non-surgical options for knee OA, clinicians should be aware of the rare but serious risk of septic arthritis. Prompt recognition and management are essential to optimize patient outcomes.