Necrotizing fasciitis (NF) is a life-threatening soft tissue infection in superficial and deep fascias. NF is most often caused by mixed aerobic and anaerobic bacteria. The treatment is early and aggressive surgical debridement, antibiotics and hyperbaric oxygen. In this case description, a nearly 60-year-old man developed NF after arthroscopic synovectomy of an infected prepatellar bursa. We stress the point that the endoscopic technique itself might be responsible for the spreading of bacteria to the fascias. This is a subject for further investigation