Infectious arthritis, also called septic arthritis, is an infection in a joint that causes arthritis-like symptoms. It is a type of inflammatory arthritis but much more severe.
Infectious arthritis occurs when bacteria or a virus enters the joint and multiplies, causing painful symptoms in and around the joint.
It is essential to diagnose and treat infectious arthritis quickly to prevent joint damage and the spread of infection.
Infectious arthritis usually affects just one joint, but it can also spread to other joints.
Despite its name, infectious arthritis is not contagious.
In this article, we look at the symptoms, causes, treatment, and recovery of infectious arthritis, and how this condition differs from another form of arthritis called reactive arthritis.
Infectious arthritis is a type of arthritis that occurs when bacteria or viruses, or other organisms get into the fluid between joints and multiply.
People are exposed to bacteria all the time, but the immune system usually removes them from the body. However, if the bacteria enter closed areas, such as the joint, they can easily multiply, causing a severe infection with inflammation and swelling.
This inflammation can break down tissues in the joint, causing permanent damage of the cartilage and bone.
A bacteria called Staphylococci usually causes infectious arthritis. This strain of bacteria also causes many other skin conditions.
Other strains of bacteria that may cause infectious arthritis include:
- Streptococcus, which cause strep infections
- Gonococcus, which cause gonorrhea
The bacteria typically reach the joint through the bloodstream.
A bacterial infection usually causes infectious arthritis, but a virus or fungus can also be responsible.
Like other forms of arthritis, the primary symptoms of infectious arthritis are swelling, pain, and stiffness in the affected joints. Other symptoms of infectious arthritis can include:
- pain that is more significant than in non-infectious inflammatory arthritis
- a limited range of motion in the affected joint
- redness, or erythema
- fever, which may be higher than in inflammatory arthritis
- changes in appetite
- increased irritability
- skin rashes
The joints most commonly affected by chronic infectious arthritis include the:
Symptoms can appear and become severe very soon after a person has contracted the infection, sometimes within a few hours. People may also experience other symptoms, depending on the organism causing the infection.
In most cases, symptoms will start to improve after a 1–2 full days of treatment. A full recovery can take several weeks, but the infection should disappear entirely.
The best treatment for infectious arthritis depends on the cause.
If bacteria are responsible for the infection, doctors will usually prescribe antibiotics. People should take antibiotics as early as possible to reduce the risk of permanent damage.
People can take antibiotics as an oral treatment over several weeks. A full course of treatment can take up to 6–8 weeks to complete.
Some people may need to spend some time in the hospital to allow continuous administration of antibiotics and to drain fluids through an IV. This treatment can last a few days or weeks, depending on the severity of the condition. Sometimes, doctors can arrange for people to have IV antibiotics at home.
Doctors may give high doses of antibiotics and may inject them to increase the speed at which they can start to take effect in the joint.
If a fungus causes the infection, doctors will treat it with an antifungal medication instead of antibiotics.
Infections caused by a virus do not respond to most treatments, usually clearing up themselves. However, doctors may use anti-viral medication in some cases, such as for infections caused by hepatitis B.
Draining the joint
In some cases, doctors may need to drain fluid from the joint as it contains harmful microbes. They can do this with a syringe or by a procedure called arthroscopy. This is where a doctor inserts a small tube into the affected joint, through a small incision.
People with infectious arthritis can also take other measures to help reduce symptoms and prevent long-term damage. People can try physical therapy or wearing a splint from time to time to support the affected joint.
However, it is essential that a person puts their joint through range-of-motion exercises to prevent the muscles or joints from shortening. This means they should not wear splints continuously.
If people do not receive treatment early enough or a sufficient dosage, there is a risk that infectious arthritis can cause permanent damage to the tissues and bones in the joint.
Without any treatment, it can also cause a severe blood infection blood called sepsis, which can be fatal.
It can also lead to an infection in the bone, called osteomyelitis.
How this damage impacts a person's life depends on which joints have been affected. For example, damage to a knee joint can affect a person's ability to stand or walk. However, surgery can usually treat this type of damage.
Anyone can contract infectious arthritis, but certain factors increase the risk of developing the condition, including:
- existing joint problems, such as other forms of arthritis
- an open wound
- intravenous drug use
- excessive alcohol use as alcohol suppresses the immune system
- a weakened immune system
- contact with non-sterilized needles
- an infection elsewhere in the body
To diagnose infectious arthritis, a doctor will carry out a physical examination, look at the symptoms, and discuss the person's medical history. If a doctor suspects infectious arthritis, they will recommend further tests.
Tests may include a blood test and taking a sample of fluid from the affected joint. Lab technicians will analyze the samples for signs of infection and inflammation and will culture the blood to make sure the infection has not spread further through the body.
The presence of harmful microbes in the fluid or unusually high levels of white blood cells in the blood can point to infectious arthritis. Sometimes, these tests show standard results, but infectious arthritis is still present. This is why doctors often take several sets of blood cultures.
Doctors may also recommend imaging tests such as X-rays or MRI scans to assess the extent of the damage already caused by the infection.
Early diagnosis is essential to prevent permanent damage to the joint.
Infectious arthritis is sometimes mistaken for a different form of arthritis called reactive arthritis.
Reactive arthritis shares the same symptoms as infectious arthritis. However, infectious arthritis is caused by an active infection within the joint, while reactive arthritis usually develops as a result of an infection in another part of the body.
However, reactive arthritis does not usually result from the infectious organism spreading to another joint. Instead, it occurs when the body's immune system overreacts to the infection, often causing joint inflammation elsewhere in the body.
Sometimes, an infection in a joint that has cleared up some time ago can trigger the autoimmune process and lead to reactive arthritis elsewhere in the body.
Infectious arthritis is a severe condition. It may cause permanent damage to the bones and tissue surrounding the affected joint.
Early and aggressive treatment can significantly improve a person's outlook.
In most cases, people make a full recovery without any lasting damage.