1)Definition of Septic Arthritis Explain Etiology explain pathophysiology (Explain pathophysiology.) Due to any etiological factor and risk factor Infection and inflammation occur and due to this synovitis (= infection and inflammation of the synovial members) and joint effusion (joint effusion) occur. The infecting organism multiplies in the synovial fluid and synovial lining. The infecting organism produces virulence factors (adhesion). Because of this, bacteria penetrate the joint and infect the joint.