Infectious arthritis, also called septic arthritis, involves a sudden, severe infection of a joint. It is a type of inflammatory arthritis that can cause swelling, pain, and tissue damage.

Infectious arthritis occurs when bacteria, fungi, or a virus infects a joint, causing inflammation. It can occur suddenly and cause intense pain, fever, and chills.

Infectious arthritis usually affects just one joint, but it can spread. As a result, it is essential to diagnose and treat it quickly to prevent joint damage and the spread of infection.

Though the name may be misleading, infectious arthritis is not contagious.

In this article, we look at the symptoms, causes, treatments, and recovery process. We also describe how infectious arthritis differs from reactive arthritis.

Share on Pinterest
Eva-Katalin/Getty Images

Infectious arthritis occurs when bacteria, fungi, or viral bodies enter the space around a joint.

A person’s immune system regularly removes these harmful pathogens from the body, but when they enter closed areas, such as a joint, they can multiply rapidly and cause a severe infection.

A 2019 review found that bacteria from the Staphylococci family cause more than half of septic arthritis cases. This strain of bacteria also causes many skin issues.

Other causes of septic arthritis include strains of Streptococci bacteria, which also cause strep infections, and Neisseria gonorrhoeae bacteria, which can cause gonorrhea.

The bacteria typically reach the joint through the bloodstream.

Infectious arthritis causes severe inflammation that can break down tissue in the joint. This may lead to permanent damage to the cartilage and bone.

Like other forms of arthritis, the primary symptoms are swelling, pain, and stiffness in the affected joint. Other symptoms of infectious arthritis can include:

  • pain that is more severe than the pain of noninfectious inflammatory arthritis
  • a limited range of motion in the affected joint
  • fever
  • fatigue
  • weakness
  • changes in appetite
  • increased irritability
  • skin rashes

The joints most commonly affected are in the:

  • knee
  • shoulder
  • wrist
  • hip
  • elbow

Symptoms can appear and become severe very soon after the infection develops, sometimes within a few hours. People may also experience other symptoms, depending on the cause of the infection.

Treatments for infectious arthritis vary depending on which pathogen is causing the condition.

Antibiotics

Because the issue can become severe, doctors typically prescribe antibiotics as soon as they suspect infectious arthritis. This may be before joint fluid testing can identify the specific pathogen involved in the infection.

In the first stage of treatment for a bacterial infection, healthcare professionals typically administer antibiotics directly into a person’s bloodstream.

If the antibiotics are effective, the symptoms may improve within 48 hours. However, a person may need the intravenous (IV) antibiotics for 2–4 weeks, depending on the severity of the condition. Sometimes, doctors can arrange for people to have IV antibiotics at home.

They may then prescribe oral antibiotics for a further 2–6 weeks.

Learn more about antibiotics here.

Antifungal medications

If a type of fungus is causing the infection, doctors treat it with an antifungal medication instead of antibiotics.

Antiviral medications

Most viral causes of arthritis are self-limiting, meaning that the condition resolves over time. However, doctors may use antiviral medications in some cases, such as in certain instances when the hepatitis C virus is involved.

Draining the joint

Doctors may need to drain fluid from an affected joint to help remove the harmful pathogens from the body. They can do this with a syringe or with a procedure called arthroscopy. This involves inserting a small tube into the affected joint through a small incision.

Exercises

People with infectious arthritis may have physical therapy to help reduce symptoms and prevent long-term damage. A doctor may also recommend wearing a splint to support the affected joint.

For anyone wearing a splint, it is essential to do range-of-motion exercises to prevent the joint muscles from shortening. A person should also not wear the splint continuously.

If a person does not receive early, robust treatment, infectious arthritis may cause permanent damage to the tissues and bones in the joint.

The effects of this damage on daily life depend on which joint is involved. For example, damage to a knee joint can affect the ability to stand or walk.

Infectious arthritis may also occur alongside osteomyelitis, which is an infection within a bone.

Anyone can have infectious arthritis, but certain factors increase the risk, including:

  • existing joint disease, such as rheumatoid arthritis
  • joint damage
  • recent joint surgery
  • skin infections
  • IV drug use

It is important to have infectious arthritis diagnosed as soon as possible. First, a doctor performs a physical examination and discusses the person’s medical history with them.

This alone does not provide enough information for a doctor to distinguish infectious arthritis from many other inflammatory conditions, so if they suspect infectious arthritis, they will recommend further tests.

These tests may require samples of blood and fluid from the affected joint. A 2018 clinical review heralded joint fluid analysis as the diagnostic gold standard for infectious arthritis.

Doctors may also recommend imaging tests, such as X-rays or MRI scans, to assess the extent of damage that the infection has already caused.

A person may mistake infectious arthritis for reactive arthritis. The two can cause similar symptoms. However, infectious arthritis results from an infection in the joint, while reactive arthritis usually results from an infection elsewhere in the body.

Some people may develop reactive arthritis following a sexually transmitted infection or an infection of the gastrointestinal tract from food poisoning.

Reactive arthritis does not typically result from an infection spreading to a joint. Instead, it occurs when the immune system overreacts to the infection, often causing joint inflammation.

Infectious arthritis is a severe condition that can cause permanent bone and tissue damage. Bacterial infections are the most common cause, although viral and fungal infections can also be responsible.

A person with infectious arthritis may experience sudden swelling, severe pain, dizziness, and fatigue.

Early and aggressive treatment, including IV antibiotics, can significantly improve a person’s outlook. If treatment begins in time, a person may make a full recovery, without any lasting damage.