A Conservative Surgical Approach to Native Knee Septic Arthritis: Is Delayed Surgery Safe? A Retrospective Cohort Study of 194 Patients

Introduction Septic arthritis requires prompt treatment to prevent joint destruction and sepsis. However, the indications and timing of surgery remain debated. Current Septic Arthritis in Native Joints (SANJO) guidelines recommend early surgical debridement, particularly in large joints. We evaluated a less invasive strategy based on initial joint aspiration and antibiotics, with subsequent intervention guided by clinical response. Methods This retrospective cohort study included patients ≥18 years treated for suspected native knee septic arthritis between January 2018 and July 2025. Only patients in whom septic arthritis was considered the most likely clinical diagnosis were included. Patients with previous surgery of the affected knee, periarticular abscess, or osteomyelitis were excluded. Results Of 803 screened patients, 194 met the inclusion criteria. Following initial aspiration, 138 patients (71.1%) required no further joint intervention, whereas 56 (28.9%) underwent a subsequent procedure. Synovial fluid cultures were positive in 45 patients (23.2%); 40 of these (88.9%) required additional intervention, including arthroscopic synovectomy in 38 (84.4%). Mean time from aspiration to additional intervention was 4.2 days. During the 1-year follow-up, recurrence occurred in 16 patients (8.2%), and in-hospital mortality was 2.6%. Conclusions A less invasive initial strategy allowed most patients to avoid additional joint intervention despite septic arthritis being the most likely clinical diagnosis. Nearly 90% of culture-positive patients required further intervention, suggesting a greater need for surgical intervention in this subgroup. These findings question a uniform 24-h surgical threshold in all clinically stable patients and support a selective, response- and microbiology-guided approach.