Introduction to native joint septic arthritis

Septic arthritis is an infection of the joint (synovial) fluid and tissues. It usually occurs spontaneously via haematogenous seeding but it can also occur following direct inoculation from instrumentation, surgery or trauma.

Septic arthritis usually presents as an infection of a single joint (ie monoarticular arthritis); however, it may involve multiple joints. An oligoarticular presentation (usually involving 2 or 3 joints) occurs in 10 to 20% of patients.

Infection in people who inject drugs often occurs in atypical sites, such as the sternoclavicular, costochondral, shoulder, vertebral or sacroiliac joints. Immunosuppressed patients may have a more indolent presentation of septic arthritis, with only mild pain or swelling.

This topic addresses septic arthritis of native joints. For septic arthritis involving a prosthetic joint, see Arthroplasty device infections.