Septic Arthritis: Bacterial Infection in a Joint

What is septic arthritis?

Septic arthritis, also known as infectious or bacterial or pyogenic arthritis, refers to the inflammation of a joint due to bacterial infection. The most common joints affected by the disorder are the knee and hip. Infants under the age of three are mostly afflicted with septic arthritis of the hip.

The affected joints may become infected with germs that enter the joint from another part of the body through the bloodstream or through a penetrating injury that brings the germs directly in contact with the joint.

Septic arthritis demandas early treatment for a positive prognosis; left untreated, it can lead to severe illness and a life-threatening condition. It may damage the cartilage and bone of the joint.

What are the causes of the disorder?

Bacteria enter a wound and travel through the bloodstream to reach the affected joint or may enter directly through a penetrating injury. The most common cause of acute septic arthritis is an infection by streptococcal or staphylococcal bacteria. Chronic septic arthritis is less common and caused by Mycobacterium tuberculosis and Candida albicans.

The risk to septic arthritis is increased in the following cases:

1. Artificial joint implants
2. Bacterial infection in another location in the body
3. Chronic condition (like diabetes, rheumatoid arthritis, sickle cell disease)
4. Drug use or injection intravenously
5. Medications that suppress the immune system
6. Joint injury
7. Recent surgery or joint arthroscopy

What one needs to know about symptoms or signs?

Symptoms of septic arthritis develop quickly and usually characterized by fever and swelling in one joint, along with pain that worsens with movement.

Symptoms experienced in children and adults include:

1. Low grade fever
2. Joint swelling and redness
3. Intense joint pain
4. Inability to move the limb with the infected joint (pseudo paralysis)

Which specialist should be consulted in case of signs and symptoms?

A person experiencing symptoms similar to that of septic arthritis must consult a specialist of infectious diseases or a joint specialist.

What are the screening tests and investigations done to confirm or rule out the disorder?

A confirmed diagnosis of septic arthritis is made through:

1. Blood tests - Blood tests can confirm the presence of bacteria in the bloodstream.
2. Imaging tests - X-rays and other imaging tests of the afflicted joint provide a detailed view of the joint and surrounding tissues.
3. Joint fluid analysis - The doctor takes a sample of fluid from the affected joint (synovial fluid) by inserting a needle in the space around the joint. Normal synovial fluid is clear and thick. However, bacterial infections alter the consistency, colour, and volume of the fluid. The collected sample is analysed in the lab to determine the causal organism responsible for the infection.

What treatment modalities are available for management of the disorder?

Treatment of septic arthritis includes:

• Medications - Once the specific microorganism causing the infection is identified, the patient is prescribed a course of antibiotic drugs, initially administered intravenously through the arm. The patient may be required to stay in the hospital for two weeks till the intravenous drug course is completed. As the condition improves, it may be switched to oral antibiotics for another four weeks. Side effects of antibiotics include nausea, vomiting and diarrhoea. Some patients also suffer allergic reactions to the drugs.
• Joint drainage - It is crucial to remove the infected joint fluid. It may be done in the following ways:
  1. Needle - The doctor may insert a needle and withdraw the infected fluid from the joint.
  2. Arthroscopy - A flexible tube fitted with a camera at the tip is inserted into the joint area through a small incision. Additional, small incisions around the joint allow suction tubes and drainage tubes to be inserted for removal of the infected fluid.
  3. Open surgery - It is difficult to drain out fluid using a needle or arthroscope from the hip joint. An open surgical procedure might be necessary in such a condition.

What are the known complications in management of the disorder?

If the antibiotic treatment is given promptly, a fast recovery can be expected. However, a delay is seeking treatment can cause permanent joint damage or joint degeneration (arthritis).

How can the disorder be prevented from happening or recurring?

People at high risk of developing septic arthritis may be given prophylactic (preventive) antibiotics.

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Sources:

"Septic arthritis," Medline Plus, https://www.nlm.nih.gov/medlineplus/ency/article/000430.htm

"Septic arthritis," NHS.uk, https://www.nhs.uk/conditions/septic-arthritis/Pages/Introduction.aspx

"Septic arthritis," MayoClinic.com, Mayo Clinic Staff, https://www.mayoclinic.org/diseases-conditions/bone-and-joint-infections/basics/definition/con-20029096

"Septic arthritis," WebMD.com, https://www.webmd.com/arthritis/septic-arthritis-symptoms-diagnosis-and-treatment