Septic Arthritis

Septic arthritis, also known as infectious arthritis or pyogenic arthritis, is a serious infection of the joints characterized by pain, fever, chills, inflammation and swelling in one or more joints, and loss of function in those joints.

The knee is by far the most commonly affected joint (- 50%) followed in order by the hip, ankle, wrist, elbow, and shoulder. The small joints of the hand and foot are infrequently affected in the absence of trauma. The majority of adults have some underlying joint abnormality, most commonly rheumatoid arthritis or osteoarthritis. Children frequently have no underlying disease. A history of trauma, intravenous drug use, or diseases that affect the immune system such as malignancy, diabetes, sickle cell disease, and chronic liver or kidney failure are red flags.

Causes

Septic arthritis develops when bacteria spread from a source of infection through the bloodstream to a joint or the joint is directly infected by traumatic penetration or surgical procedures. The onset of the symptoms is usually rapid with joint swelling, intense joint pain, and low-grade fever.

The cause of septic arthritis in babies and young children is usually staphylococci, hemophilus influenzae, and gram-negative bacilli.

Symptoms

• Swelling
• Joint pain
• Decreased mobility
• Fever ++

Signs

• Erythema, warmth, and joint effusion are usually present but are neither sensitive nor specific for the nature of the arthritis.
• Fever ++
• Monoarticular ++++
• Polyarticular ++
• Most specific sign is limitation of active and passive movement of the joint, but its absence cannot be used to reliably exclude septic arthritis, particularly in very mobile joints such as the shoulder.

Treatment

The increase of synovial fluid in the joint that occurs because of the infection requires aspiration (using a needle and suction to remove the liquid) to relieve the pressure and to obtain material to culture the specific pathogen. In more severe cases, surgery may be needed to drain the fluid.

Treatment is with antibiotics. The exact antibiotic used will depend on the microorganism that is cultured from the synovial fluid. The choice of antibiotic will depend on which are active against your bacteria and how effective the antibiotics are at getting into the joint space where the infection is.