Pyogenic arthritis, which is sometimes called septic arthritis is a suppurative inflammation within a joint space, most commonly due to haematogenous spread, but sometimes due to direct spread from a penetrating wound or a neighbouring infection, for example chronic osteomyelitis. Most commonly affected are children, premature neonates, the elderly and the immune suppressed. Generally, this disease is monoarticular, and occurs often in the knee and the hip, but may involve any joint. In infants there can be multiple joint involvement. Note that septic arthritis of the hip may present as pain in the knee and vice-versa.