Objective and design: Lyme arthritis is characterized by strong inflammatory reactions probably due to the presence of Borrelia burgdorferi in the joint. It has been suggested that Borrelia adopts different molecular mechanisms that either can amplify the host’s inflammatory response or can suppress it. In the present study we analyzed the induction of matrix metalloproteinases (MMPs) and cyclooxygenases (COXs) in human synoviocytes exposed to different B. burgdorferi sensu stricto isolates (Geho and B31).