Bacterial joint infection (septic arthritis)

Bacterial joint infection, also called septic arthritis, is an infection inside a joint. Bacteria can rapidly damage cartilage and enter the bloodstream. Prompt assessment, joint fluid sampling, antibiotics and usually drainage are needed.

• One large joint often suddenly becomes very painful, warm and swollen, for example the knee, hip, shoulder or ankle.
• Moving or putting weight on it is very painful and may be almost impossible.
• Fever may occur but is sometimes absent in older people, young children or those with reduced immunity.
• An infected artificial hip or knee may begin more subtly, with increasing pain or wound leakage.
• Investigation usually involves joint aspiration, cultures and blood tests. Imaging alone cannot rule out infection.
• Antibiotics often start immediately after samples are collected for culture; in severe illness, sometimes even earlier.
• The joint is drained and washed out with a needle or surgery when pus or a large amount of inflammatory fluid is present.
• Do not wait at home with an acutely hot, swollen and very painful joint, especially with fever or feeling ill.