Infectious Arthritis

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Basics of Infectious Arthritis

Infectious arthritis is a form of arthritis that is produced by an infection. It is also called "septic arthritis."


An infection is an illness that is caused by certain types of germs. There are three major kinds of germs that can cause infections: bacteria, viruses or fungi.

Normally, these germs are not found in a person's body. They can live in the air in uncooked food, plants, soil, animals or trash. When they enter a person's body these germs generally cause the person to become sick. Doctors call an illness that is directly caused by any one of these germs an "infection."


Arthritis means joint inflammation ("arthr-" = joint"; "-itis" = inflammation). There are over 100 kinds of arthritis. How does a person know if he or she has inflammation in a joint or another part of the body? Generally, that area becomes warm, painful, swollen, red and/or stiff.


Unlike other types of arthritis, infectious arthritis is usually not a long-term illness. Treated promptly and properly, it is generally a curable form of arthritis. However, without proper treatment, infectious arthritis can result in serious damage to the joints involved and may spread to other parts of the body. That's why it is important to recognize the symptoms of infectious arthritis and get prompt treatment.


Infectious arthritis may occur without any other infection present. However, it is usually the result of a previous infection. A germ first causes an infection elsewhere in the body, then spreads to one or more joints to produce infectious arthritis.

A germ can enter through almost any place in a person's body. The most common places of entry are a person's skin, throat, ears or nose. Once inside the body, the germs can get into the blood stream. From there they can travel to the person's joints (or any place that is suitable for them to live). Sometimes a bacterium, virus or fungus can enter a person's joint directly through a wound.

Most often, only one joint is affected. Sometimes two or three joints become involved. The large joints are most often infected especially the shoulders, hips and knees, although other joints can also become involved.

Sometimes a condition called erythema nodosum can occur along with an infection. Although it is most often associated with tuberculosis and infections by certain fungi, it is not due directly to these infectious germs. The most noticeable symptom of erythema nodosum is red tender bumps about the size of a quarter--in the skin of the lower legs and sometimes on other parts of the body. Other symptoms that may appear include inflammation of the ankle (and sometimes other joints) and fever.

Causes of Infectious Arthritis

Infectious arthritis may be caused by bacteria, viruses or fungi.


Most types of infectious arthritis are caused by bacteria. There are many different kinds of bacteria that produce a variety of infections. Bacteria that can cause infectious arthritis include: gonococcus, certain Gram-positive bacteria, certain Gram-negative bacteria, spirochetes, and tuberculosis. Descriptions of these bacteria and the symptoms they produce are listed below.


Gonococcus is the name of the bacterium that causes gonorrhea. Gonorrhea is a sexually transmitted disease. It primarily affects the genital area. However the gonococcus bacterium can travel through the blood stream to other parts of the body. If it settles in one or more joints, infectious arthritis can develop in those joints and the area that surrounds the joints. Gonococcus generally affects the knee joints and can also affect the tendons and bursae to cause tendonitis and bursitis.

This infectious arthritis can occur within days or weeks after the symptoms of gonorrhea appear. It occurs more often in women than in men. The symptoms of gonorrhea are not as obvious for women. Therefore, women generally seek treatment later than men. This delay in treatment gives the bacteria more time to travel through the bloodstream.

Symptoms of infectious arthritis caused by gonococcus may include:

  • fever
  • chills
  • abdominal pain in women
  • discharge from the penis or vagina
  • rash which appears as a few red rimmed dime-sized pus filled spots that are raised in the center
  • inflammation of the tendons (bands that connect bones to muscles)
  • arthritis which develops in joints such as the knees or wrists

This type of arthritis should be treated immediately--as soon as you notice symptoms--to prevent serious damage to the joints.

Gonorrhea is spread from person to person by sexual contact. Therefore care should be taken in sexual relationships where there may be a chance of getting the disease. The spread of gonorrhea can usually be prevented by the correct use of condoms. Anyone who thinks he or she may have gonorrhea should see a doctor as soon as possible. Appropriate treatment with antibiotics can prevent damage to joints and other parts of the body.

Gram-positive bacteria

There are several different kinds of Gram-positive bacteria. They are called Gram-positive because when mixed in the laboratory with a solution called "Gram's stain," they take on a bluish-purple stain or color. Some of the Gram-positive bacteria that can cause infectious arthritis are: staphylococcus, streptococcus, and pneumococcus.

These Gram-positive bacteria cause other illnesses such as meningitis, pneumonia, or an abscess. Often people with these illnesses develop infectious arthritis when the bacteria spread to a joint and produce inflammation. In other cases, Gram-positive bacteria cause infectious arthritis, but no other illness is detected.

Staphylococcus is the second most common cause of infectious arthritis. It is often called a "staph infection." A staph infection can occur as a result of a skin or sinus infection or after surgery. People who have rheumatoid arthritis or who take steroids or immunosuppressive agents (such as imuran, cytoxan and methotrexate) are more apt to get infectious arthritis from staphylococcus bacteria.

Symptoms of a "staph infection" in a joint may include:

  • fever
  • redness, swelling, extreme tenderness occurring in a single joint
  • pus (yellowish-white substance) draining from a wound or abscess

Gram-Negative Bacteria

These bacteria are called Gram-negative because they do not take on a bluish-purple color when mixed with the Gram's stain. They are less likely to produce infectious arthritis than Gram-positive bacteria. Gram-negative bacteria commonly infect people whose bacteria-fighting defense system (immune system) is already weak.

Hemophilus is a Gram-negative bacterium that causes severe sore throat and meningitis. It is a major cause of infectious arthritis in infants but rarely causes it in adults.

Spirochete- Lyme Disease

Spirochetes are bacteria that appear spiral shaped under a microscope. There are many different kinds of spirochetes. One kind (called Borrelia) causes a form of infectious arthritis called Lyme disease. This disease occurs in people as a result of a tick bite. Anyone can get Lyme disease but it is more common in children.

The Borrelia spirochete is carried by a small tick (called Ixodes) that lives on deer and mice. It is found in wooded areas during the spring and early summer. Many areas of the country have reported cases of Lyme disease. However most cases occur in seven states: New York, New Jersey, Rhode Island, Connecticut, Massachusetts, Wisconsin and Minnesota.

People infected may not have seen the tick because it is very tiny. It is oval, has eight legs and is often no larger than a pinhead or match head.

When the tick bites someone, it injects the spirochete into the person's blood stream. Symptoms of the infection usually do not appear until 1-3 weeks after the bite.

You may want to protect yourself and others from Lyme disease when you visit wooded or lake areas as suggested below.

The following measures may help prevent tick bites:

  • wear long sleeves and pants
  • pull socks over pant legs
  • wear closed shoes
  • wear a hat
  • use tick repellent on clothes
  • shower afterwards and inspect for ticks particularly checking arms, legs and hairline

Symptoms of early Lyme disease include:

  • Skin rash which is 5-20 inches in diameter. It is white in the center and bright red on the outside. The center is hard and hot to touch. It may occur around the bite and on different parts of the body. It may last up to a month.
  • Flu-like symptoms of fever and chills, fatigue, headache, vomiting and soreness all over.
  • Joint pain and swelling usually in the knees and sometimes also in the hips, shoulders and ankles.
  • Sore throat, dry cough, stiff neck, swollen glands.
  • Dizziness and sensitivity to sunlight.

If untreated, the spirochete may spread to the person's brain, heart and nervous system. This could lead to symptoms such as:

  • temporary paralysis of the face
  • numbness and tingling in the hands or feet
  • severe headaches, depression, memory lapses
  • poor muscle coordination
  • heart problems.

With proper medication, Lyme disease usually goes away in a short time. However, if not diagnosed and treated properly, symptoms can become more severe and recur several times over a year or more.

Tuberculosis Bacteria

The bacterium that causes tuberculosis can also cause infectious arthritis. It is much less common today than it was years ago. When it does occur, it is often very slow to develop and usually spreads from the lung to involve only one joint.


Infectious arthritis can also be caused by viruses. It is usually produced by a viral infection that is already present in a person's body. Infectious hepatitis, mumps and infectious mononucleosis are viral infections that can lead to a short bout of infectious arthritis. Generally, the joint inflammation lasts no more than one to two weeks. German measles can also produce an infectious arthritis which may occasionally last as long as one year after the measles rash is gone.


Fungi are the least common cause of infectious arthritis. Arthritis produced by a fungus usually develops very slowly. Types of fungi that can produce arthritis are usually found in soil, bird droppings and certain plants (especially roses). Chicken farmers and gardeners are especially likely to be exposed to this type of arthritis.

Differences between types of infections

Bacterial, viral, and fungal infections are different from each other in the following ways:

Bacterial infection:

  1. Generally located in one place or area
  2. Usually accompanied by fever and shaking chills
  3. Usually begins quite suddenly
  4. Usually cured by taking antibiotics

Viral infection:

  1. Ache all over
  2. Usually mild or no fever
  3. Not cured by antibiotics
  4. Usually goes away on its own

Fungal infection:

  1. May be in one area or throughout the body
  2. May have low-grade fever or none at all
  3. Usually begins quite slowly over weeks or months
  4. Usually treated with anti-fungal medication

Can periodontal surgery cause infectious arthritis?

Any significant manipulation of the gums can cause bacteria to enter the blood stream--even brushing the teeth in the presence of gum disease. Periodontal health is important. In rare cases, periodontal disease may cause an infectious arthritis, especially when extensive dental work is being done. We worry about it in particular for those with artificial joints in place as they can not combat the bacterial that might get into the blood stream. Infectious arthritis occurs more frequently in people with abnormal joints, especially rheumatoid arthritis, people with artificial joints or those with diabetes. For those with arthritis or artificial joints in place, consult your rheumatogist or orthopedist before having dental work done. An antibiotic 1 hour before and 8 hours after may be in order.

Diagnosis of Infectious Arthritis

To determine if a person has infectious arthritis, the doctor will first ask about the person's symptoms and any other medical conditions.

The doctor will want to know about any recent travel, illness or contact with people who have had infections. Work or home conditions might also give the doctor clues about the illness.

After the medical history, the doctor will do a physical exam and order special tests. X-rays may be taken to determine if there is joint damage. Various laboratory tests can be done to find out if an infection is present.

It is most important to identify the specific germ causing the infection. Bacteria and fungi can usually be identified from joint fluid, blood, urine or the infected area. The doctor will almost always want to remove and examine fluid from the infected joint. If tuberculosis or fungi are suspected, it will be necessary to remove a tiny piece of tissue from the joint. This is called a biopsy. In the laboratory, the fluid or tissue will be examined under the microscope to determine what kind of bacteria or fungi are present.

A viral infection is usually diagnosed by a person's symptoms and medical history. After the infection has been present for weeks or longer, blood tests may show the presence and amount of a person's own virus-fighting proteins (antibodies) in response to a viral infection.

Treatment of Infectious Arthritis

Most often people with infectious arthritis need to go into the hospital for diagnosis and treatment; the treatment and length of stay will vary depending on the type of infectious arthritis present.

Treating bacterial infections

Almost all people whose infectious arthritis is caused by bacteria are given an antibiotic. Antibiotics are medications that fight off bacteria. Different antibiotics destroy different bacteria. Therefore, the antibiotic prescribed depends on the type of bacteria present.

Antibiotics can be taken by mouth or given through the person's vein. When given through a vein it is called an intravenous or IV injection. An IV releases the antibiotic directly into the bloodstream. This allows the infection-fighting drug to travel faster in higher concentration and directly to the infected joint.

Often antibiotics can destroy an infection in a few days or weeks. In some cases, antibiotics must be taken over several months. Remember to take antibiotics for the number of days prescribed--even if symptoms disappear. Many people think they can stop taking the medication when the symptoms are gone. Even though symptoms disappear, bacteria may still be present. If not destroyed by the antibiotic, the bacteria can re-infect the area.

Treating viral infections

Generally, infectious arthritis caused by a virus goes away by itself. Medications are not available to treat viral infections. Resting in bed and drinking plenty of liquids are usually recommended.

Treating fungal infections

Fungal infections are often difficult to treat. Doctors can prescribe a fungus-fighting medication. This may need to be used for months. Surgery is sometimes performed to clean out the infected joint. Fungal infections are difficult to eliminate entirely. Even after successful treatment, they may recur.

Treating inflammation

For all types of infectious arthritis, the doctor may prescribe a medication to relieve pain and inflammation. These are called anti-inflammatory drugs.

In many cases, the doctor may need to drain one or more joints. This is done by inserting a needle into the joint and withdrawing fluid. This procedure is generally easy and usually not painful. It is done to remove any harmful substances released by the bacteria or by the body's bacteria fighting cells. Joint fluid drainage may need to be done several times. Most of the time, repeated drainage along with high doses of IV antibiotics can prevent the need for surgery.

Other treatments

Arthritis treatment may also include resting and protecting the joints. Splints can be used to limit movement. This helps reduce pain and tissue damage.

After the infection is gone, the doctor will frequently recommend exercises to build up muscle strength. Other exercises may be recommended to increase the joint's range of motion. A physical therapist can demonstrate and assist with exercises that can be done at home.

Summary of infectious arthritis

  • Infectious arthritis is a form of arthritis that is caused by bacteria, viruses or fungi.
  • Many different types of infections can produce joint inflammation. This type of arthritis is almost always curable.
  • If the infection is diagnosed and treated promptly, there is usually no lasting joint damage. If the infection is not treated early, permanent joint damage may result. Bacterial and fungal infections are usually treated with medication. A viral infection will generally go away on its own.
  • Most often people with infectious arthritis are able to resume their normal activities once the infection is gone.


Some of this material may also be available in an Arthritis Foundation brochure. 

Adapted from the pamphlet originally prepared for the Arthritis Foundation by Frank R. Schmid MD. This material is protected by copyright.

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