Infectious Arthritis: Symptoms and Treatment

Infectious arthritis or septic arthritis, as the name suggests, is an inflammation in the joints due to a local infection of the joint space and fluid. The infection may be caused by bacteria, viruses, or fungi. The most common organism known to cause septic arthritis is the bacteria Staphylococcus aureus. Frequently an infection elsewhere in the body reaches the joint through the bloodstream. In addition, penetration of the joint space during procedures, surgery, or trauma can directly deposit microbes within the joint leading to infection.

Risk Factors for Infectious Arthritis

• Old age, increased risk in those > 80 years
• Immunodeficiency
• Diabetes Mellitus
• Skin infection
• Recent joint surgery or procedure
• Prosthetic joint
• Intravenous drug use
• Alcoholism
• Rheumatoid Arthritis

Symptoms of Infectious Arthritis

• The single joint is involved – most commonly the knee
• Pain, swelling, warmth, and redness of the involved joint
• Decreased mobility of the joint
• Fever is present often with chills

Diagnosis of Infectious Arthritis

The diagnosis is suspected based on the history and examination finding of a single, swollen, and painful joint with restricted movement. The following tests help to confirm the diagnosis

• Synovial fluid aspiration: The synovial fluid is the fluid in the joint space. This fluid is aspirated using a needle inserted into the joint cavity after administering local anesthetics. An ultrasound may be used to guide the needle. The fluid is analyzed for white blood cells, stained for bacteria, and cultured for bacterial growth.
• Blood culture: This will assist in looking for a bloodstream infection
• Blood tests to look at the complete blood count and inflammatory markers such as Erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP)
• Imaging of the affected joint: X rays, CT, and MRI may be done to look closely at the joint and is used for monitoring response to treatment.
• Echocardiography: If suggested by clinical features and blood cultures, individuals with staphylococcus aureus infectious arthritis are recommended to get an echo (imaging of the heart using ultrasound rays) to look for infective endocarditis. This is a condition with infective growth over the heart valves and could be the source of organisms in this case

Treatment of Infectious Arthritis

Infectious arthritis is treated through a combination of antibiotics tailored to the responsible organism and drainage of the infected joint fluid

• Antibiotic therapy: The individual is usually prescribed injectable antibiotics for 2 weeks followed by oral antibiotics for another 2 weeks. The choice of antibiotics is dependent on the findings of the synovial fluid microscopy and culture.
• Drainage of the joint: The infected fluid needs to be released to aid in healing. The joint is drained using a needle for aspiration, through surgical drainage procedures.

Complications of Infectious Arthritis

• Destruction of the joint: the infection can lead to complete destruction and degeneration of the tissues in the joint space. This can lead to loss of movement of the joint.
• Osteomyelitis: This is an infection of the bone. The infection in the joint space can cross the joint lining and reach the bone to cause infection

Prognosis of Infectious Arthritis

After receiving treatment, the outcomes are uncertain. The infection is generally cleared successfully with appropriate antibiotic therapy. In some, the infection continues to destroy the joint. Even after the complete resolution, a residual restriction of joint movement may remain. Severe infectious arthritis may also lead to death in individuals who are old, frail, and immunocompromised.

References:

• Shirtliff ME, Mader JT. Acute Septic Arthritis. Clin Microbiol Rev. 2002 Oct;15(4):527–44.
• García-Arias M, Balsa A, Mola EM. Septic arthritis. Best Pract Res Clin Rheumatol. 2011 Jun;25(3):407–21.