Suppurative Arthritis- involves a single joint- most commonly the knee (< hip < shoulder, axial joints in drug users)- H. influenza arthritis < 2 year olds- S. aureus in older children/adults- Gonococcus during late adolescence/young adulthood- Salmonella in individuals with sickle cell diseases

Mycobacterial Arthritis- monoarticular- granulomas with central caseous necrosis

Lyme Arthritis- Borrelia burgdoferi (transmitted by ticks)- knee joint

Viral Arthritis- HIV, influenza, echovirus, parvovirus B19, EBV, hepatitis B and C viruses- acute symptoms